Research for Sports Therapists

Welcome to the Research for Sports Therapists online learning tool. You will be directed to review these sections following the delivery in the lectures.

Use these courses to gain an insight into what you have learnt from the lectures and pre reading. You can attempt the assessments as many times as you wish; just log in with your UCB email address.

Assignment 1 - Literature review

Assignment 1 - Literature review

Assignment 1 - Literature review

  • —Literature review on a sports therapy concept or treatment modality. See below for full scope of assignment
  • —Incl. concise methodology
  • —1500 words
  • —Critical appraisal of the literature
  • —CURRENT literature
  • —Highlight the gaps within the literature

Assignment remit (Scope of the review):

This assignment should be conducted about a contemporary sports therapy topic e.g. Maitland mobilisations in the treatment of low back pain; effect of ice on joint position sense; effect of caffeine on repeated sprint performance etc.  There should be specific analysis of the current research base and potential ‘gaps’ within the literature.

Recommended format

  • Introduction
  • Methodology
  • Discussion and conclusion
  • Appendix (Literature matrix)

Introduction

The introduction section should have a 'hook' to gain the attention of the reader. For example, why did you choose the topic and why is it important.

Task

Read the following article: Effect of ankle proprioceptive training on static body balance (http://tinyurl.com/z9dc4p4) and pay attention to the structure of the introduction section.

What did the first two sentences state?

The ankle joint is in close proximity to the body’s base of support, thus playing an integral role in maintaining balance. Stability of the ankle joint is paramount when considering regulation of balance.

These first two sentences have given the reader some useful information and are clearly a hook. They are not too detailed or specific, but general comments relating to the ankle and how it is important for balance.

The main body of the introduction explains in more detail about the specific nature of the topic:

Considering this knowledge, the findings of the related literature samples suggest that ankle proprioception is closely related to balance control and that balance is negatively affected by impaired ankle proprioception after injuries. However, the results of studies investigating the effects of proprioceptive training on body balance, or vice versa, are conflicting. Powers et al. investigated the effect of 6 weeks of strength and proprioception training on measures of muscle fatigue and static balance in subjects with unilateral functional ankle instability (FAI) and found that there were no significant effects of strength or proprioception training on these measures. Rozzi et al. suggested that 4 weeks of balance training was effective in improving joint proprioception and single-leg standing ability in subjects with unstable and non-impaired ankles.

The end of the introduction should give a clear indication of what you are going to discuss. Here is the final paragraph of the above article.

Considering the above-mentioned knowledge about the close relationship between ankle proprioception and balance, and the conflicting results of the literature samples, the present study aimed to investigate the effect of ankle proprioceptive training on static body balance in healthy individuals.

There is a clear statement of the direction of the review and it leaves the reader in no doubt what will be discussed. Make sure that you final sentence is clear and specific to the assignment.

Methodology

A brief methodology to include the following:

  • Literature sources i.e. PubMed, Medline, UCB Online
  • Types of literature used in the review
  • Key search terms used
  • Search techniques i.e. Boolean operators
  • Scope e.g. date range
  • Use of analysis tool e.g. CASP or PEDro

Read the methodology section of this article: Effects of proprioceptive exercises on pain and function in chronic neck- and low back pain rehabilitation: a systematic literature review (http://tinyurl.com/jltjj37).

Only randomised controlled trials were included for this systematic review (SR). Titles retrieved from electronic search, were screened by two authors (MM and CS). To qualify as an eligible study, participants had to be of adult age (>18 years), present with chronic non-specific musculoskeletal neck- or low back pain (at least three months), including whiplash-associated disorders. Only studies declaring clinical examination or interview assessment of pain were included. Exclusion criteria were neurological deficits related to peripheral or central nerve damage, vestibular diseases, osteoarticular diseases (e.g. rheumatoid arthritis), fractures, and tumours. No restrictions regarding gender, ethnicity, language, or clinical setting (in-patients or out-patients) were made. Pain during or after pregnancy, complex regional pain syndrome, headache alone, and fibromyalgia were also added to the exclusion criteria.

The methodology section should tell the reader how you did the review and how you analysed the results. Make sure that you include all the relevant detail given to you in the assignment remit.

Discussion

Note: It is recommended that you use headings to signpost your work.

You should write the literature review in a narrative style and avoid treating each study independently.  Identify key areas from each study that you wish to discuss and compare within paragraphs.

For example, you may wish to discuss the effects of soft tissue therapy on exercise induced muscle damage.  Within the main body, you may choose to separately discuss the duration of the massage; type of massage; effects on ratings of pain; markers of muscle damage e.g. creatine kinase (CK) etc.  Each paragraph should have an introduction, discussion and conclusion.

Finally, try and create a transition (link) to the next paragraph.

Note: The length of this section should normally be about 80% to 85% of your word count.

Read the following paragraph from an article discussing the effects of cryotherapy on joint position sense in healthy participants:

Three of the groups (Wassinger et al., 2007; Dover & Powers, 2004; Ozmum et al., 1996) that administered a superficial ice application reported no change in JPS posttreatment. Dover and Powers (2004) and Wassinger et al. (2007) both applied cubed ice, contained in a bag, for durations of 30 minutes and 20 minutes, respectively, to the shoulder. Although Wassinger et al. (2007) reported no differences in positional error after the ice application, they noted a decrease in movement patterns and throwing accuracy after treatment. Similarly, Ozmun et al. (1996) applied an ice pack to the knee for 20 minutes, but they did not state if their ice packs were commercially available or constructed by them specifically for this purpose. Also, the focus of Ozmun et al. (1996) appeared to be on movement reproduction pattern and not joint angle reproduction. All the researchers reported their result in degrees (Dover & Powers, 2004; Uchio et al., 2003; Surenkok et al., 2008; LaRiviere & Osternig, 1994; Ozmum et al., 1996) except Wassinger et al. (2007) who reported positional error in centimeters of vertical displacement.

This paragraph highlights how the author is able to demonstrate a breadth of knowledge (number of studies reviewed) and some critical analysis of some key areas. In this case, the author is discussing the differences in ice application and the effects on joint position sense. The authors then discuss the use of ice packs and if they were commercially available or self constructed. Finally, they discuss the units reported in the results e.g. degrees or centimetres.

Writing in this narrative style allows you to synthesise a number of articles and compare key points within one paragraph. This is seen as a more academic writing, as opposed to writing about each study in a separate paragraph.

You should aim to identify key aspects of the studies that may support or refute each other and discuss in relation to their findings.

Conclusion

Conclude by highlighting the major thrust of your answer. Summary of the main major points, highlighting the core findings, arguments or conclusions. This could be supported by bringing the mini-conclusion for each key point together. Do not introduce new ideas which were not discussed in the main body.

Note: The length of this section varies, normally about 10% to 15% of your word count.

Read the following part of the conclusion in relation to the cryotherapy study:

In the 7 studies we reviewed, 3 joints were assessed (shoulder, knee, and ankle) in a combined 204 healthy participants after a cryotherapy intervention. Four groups found cryotherapy to have no effect on JPS, whereas 3 others found JPS reduced after a cryotherapy treatment. Because of differences in the joints being assessed, the modality of cooling, measurement techniques, and quality of the reviewed studies, further research is needed before a conclusive answer as to whether cryotherapy reduces JPS can be determined. Given this brevity of research, we are also unable to make a recommendation as to when athletes can safely return to participation after treatment. Despite the suggested benefits of cryotherapy, until further evidence is provided, athletic trainers and clinicians should be cautious when returning individuals to physically demanding or dynamic tasks after cryotherapy.

 

The authors have summarised the key points and given a clear conclusion and subsequent recommendations relating to the efficacy of cryotherapy. This gives the reader a clear indication of the main thrust of the work and future developments. You should aim to do this within your conclusion section.

Q1. How many words should the literature review be?

  • 2000
  • 1500
  • 3000

Q2. You must add your literature matrix as an appendix

  • True
  • False

Q3. The recommended format of the literature review is

  • Introduction
  • Methodology
  • Discussion and conclusion
  • Appendix
  • All of the above

Q4. A hook is used for what purpose?

  • Throw the reader off the main topic of discussion
  • Gain attention of the reader

Q5. The first few sentences of the introduction are normally

  • Generic
  • Specific

Q6. The end of the introduction should not allow the reader to know what you are going to discuss

  • True
  • False

Q7. The methodology should include the scope of the review i.e. dates searched

  • True
  • False

Q8. The methodology should tell the reader

  • How you did the review
  • How you analysed the results
  • Both

Q9. Headings are recommended in the main body of the literature review

  • True
  • False

Q10. You should try and write in a narrative style.

  • True
  • False

Q11. A link to a subsequent paragraph is known as

  • Transition
  • Translation
  • Transatlantic
  • Transcutaneuos

Q12. Breadth of knowledge can be demonstrated by

  • A number of studies reviewed
  • Discussion of topics that are not related to the assignment title

Q13. A summary of the main thrust of your review is found in

  • Introduction
  • Methodology
  • Conclusion

Q14. New ideas are introduced in the conclusion

  • True
  • False

Q15. Future studies are not recommended in this section

  • True
  • False

Assignment 2 - research proposal

Assignment 2 - research proposal

Assignment 2 - Research proposal

In groups of 4, you are to present a research proposal based upon a contemporary sports therapy topic.

Areas covered must include:

  1. Introduction to the research topic, including:
    1. Rationale
    2. Previous research
    3. Gaps in the literature
  2. Methodology, including:
    1. Participants e.g. age, gender etc.
    2. Equipment - validity and reliability
    3. Ethical considerations
    4. Statistical analysis
  3. Results, including:
    1. Dummy data analysis - use of Minitab or Excel
    2. Appropriate presentation of the results
  4. Discussion, including:
    1. Discuss the implications of the study in a wider sports therapy context
    2. Demonstrate an understanding of alternative or future developments in the subject area

This is your opportunity to demonstrate that you are able to formulate a research proposal for a primary project. Therefore, you must include all of the above sections.

Introduction

In this section, you should demonstrate that you have read around the subject and identified gaps in the literature. For example, you may have initially looked at the effects of caffeine on vertical jump height. During your reading, you identified that there was a range of caffeine used and a lack of evidence for female basketball players. Therefore, your study may look at the effects of caffeine on vertical jump height in female basketball players (Do not use this in your presentation!)

Better marks for this section will be awarded for the range of literature that you have read and the critical appraisal of aspects of the numerous methodologies.

Methodology

A good methodology would enable another sports therapy student/staff to replicate the study without asking any questions. Make sure that you include the four sections outlined above. You will need to justify the equipment you are using i.e. is it measuring what you want it to measure and in a reliable manner? All ethical considerations need to be addressed and should include all the necessary paperwork. Finally, you need to include the statistical analysis that you will be using and the justification for it.

Results

The aim of this section is to present the findings of your study in an appropriate manner. You will be awarded marks for the construction and correct labelling of tables or figures. You also need to state the results of the study i.e. was there a significant difference. You do not need to include all of the raw data, just a summary.

Discussion

In the discussion, you need to show that you understand the implications of your findings in context of sports therapy. For example, you have showed that female basketball players increased their vertical jump height after ingesting 4 mg of caffeine per kg of body mass. How does this relate to the role of a sports therapist? What would the take home messages be for the reader of your study?

Finally, you need to discuss future studies that are apparent following your results. In the case of the basketball and caffeine study, you may wish to look at other areas of anaerobic performance, different dosages or different timings of ingestion.

Q1. How many sections make up the research proposal?

  • 1
  • 2
  • 4
  • 5

Q2. Gaps in the literature are presented in which section?

  • Discussion
  • Results
  • Introduction

Q3. Critical appraisal of the literature is presented in which section?

  • Introduction
  • Results
  • Methodology

Q4. The validity and reliability of equipment used in your study should be in which section?

  • Methdology
  • Results
  • Introduction

Q5. The age, height and mass of participants should be presented as the mean plus standard deviation

  • True
  • False

Q6. Dummy data is presented in which section?

  • Methodology
  • Results

Q7. Tables and figures can be used to graphically present your findings

  • False
  • True

Q8. Future studies should be given in which section?

  • Results
  • Discussion

Q9. Understanding the implications of your findings is an important aspect of the discussion

  • True
  • False

Q10. Minitab of Excel can be used for statistical analysis

  • False
  • True

Understanding academic sources

Understanding academic sources

Different types of academic sources

Peer review definition (Oxford Dictionaries, 2016)

Evaluation of scientific, academic, or professional work by others working in the same field:  we submit our findings to rigorous peer review.Click on the links to the following journal articles and write down the following for each:

  1. Was the title clear i.e. was there an identifiable aim?
  2. What differences did you notice between the articles?
  3. How were the sections arranged?
  4. How many references were listed?

Free access articles:

  1. Cryotherapy and joint position sense in healthy participants: a systematic review

  2. Classification and grading of muscle injuries: a narrative review

  3. Strength-Training Protocols to Improve Deficits in Participants With Chronic Ankle Instability: A Randomized Controlled Trial

  4. Implementation of a strength training program for a 5-year-old child with poor body awareness and developmental coordination disorder

  5. Expert opinion: diagnosis and treatment of proximal hamstring tendinopathy

Literature matrix

Once you have identified a number of articles that you wish to use in your assignments or for revision purposes, it may be useful to organise them for ease of review. One recommended method is to use a literature matrix. The literature matrix is easy to formulate, you just need to fill in some boxes. The information within these boxes should help you identify areas for discussion in the main body of your text. The recommended format is below:

Table 1. Recommended PICO format.

Author/

date

Population Intervention Comparator Outcome(s)

Smith et al.

2016)

25 (f) recreationally trained

6 weeks HIIT training

>85 VO2max

60s:120s

Control group - continue with normal training Sig increase in VO2max. No diff in 30m sprint time for both groups.

Thomas

(2014)

15 (m) elite football players

4 weeks SIT >95% HRmax.

30s:60s x 12

No control group Sig decrease in 40m sprint time.

 

PICO

PICO is used to help you formulate an answerable question. For more information, click on the link.

Population

—Should be relevant to the population to which the review findings will be applied e.g. female elite endurance athletes

You can broaden the population (sub groups) if you will report the differences between them e.g. male arthritis adolescent vs. elderly; female elite vs. non-elite swimmers.

Intervention

—Factors usually specified include the precise nature of the intervention e.g. static stretching; ultrasound; caffeine etc.

Comparator

—Specify if a comparator or alternative treatment has been used e.g. dynamic stretching; water; placebo etc.

Outcome(s)

Primary outcomes e.g. significant differences between groups.

Reviewing and critiquing the literature

Reading: Hall and Getchell (2014) - chapter 3.

In this section, we will discuss how you comment and summarise key aspects of studies in a narrative style. Your ability to write a literature review is important, most of your assignments are based around summarising a sports therapy topic.

Published literature review papers are valuable because they enable the reader to become familiar with a topic without having to identify, collect and read multiple papers on that topic (Hall and Getchell, 2014)

To help you gain an understanding of review articles, click on the following sports therapy related topics:

  1. A systematic review and meta-analysis of clinical trials on physical interventions for lateral epicondylalgia.

  2. Neurological consequences of traumatic brain injuries in sports.

The goals of the literature reviews may vary. Some may be written to present recent findings of a contemporary topic (traumatic brain injuries for example). Other may want to present the development of a particular line of research. Literature reviews may present opposing viewpoints of a topic or they may support a particular perspective.

Q1. A literature matrix helps organise your journal articles

  • True
  • False

Q2. It is recommended that you use PICO to help formulate an answerable question

  • True
  • False

Q3. PICO stands for

  • Potential, Interesting, Coherent, Objective
  • Population, Intervention, Comparator, Outcome(s)
  • Population, Intensity, Cohort, Operation

Q4. The outcome section of PICO highlights the primary outcomes of a study

  • True
  • False

Q5. A literature review should be written in a narrative style

  • True
  • False

Q6. What may be the goals of a literature review?

  • Present recent findings
  • Present development of research
  • Present opposing views
  • Support a particular perspective

Writing the review

Writing a literature review

Structure of the review

Introduction

This section should be concise and ensure that the reader knows exactly what you are going to discuss in the main body of the literature review. It should cover the following:

  • Generic sentences to place your work into context
  • More specific sentences to highlight the areas of interest that you will be discussing
  • Clear definitions of basic concepts

By the end of the introduction the reader should be left in no doubt about the topic.

Consider the following three introduction sections of an academic journal:

1.2.3.What do all of these opening paragraphs have in common? They each set out to introduce the topic, primarily in quite a broad sense, but are linked to the title of the work. Note that they are all referenced.

Now that you have written the first sentence, you need to add a few more.  Remember, we are looking for you to demonstrate a broad knowledge base (what you have read) and a depth of understanding (analysis of what you have read).  Both of these areas may contribute to a higher grade.

The subsequent sentences normally follow a pattern too.  These sentences usually give more specific detail and may highlight some key areas that will be discussed later in the assignment.  We will use the third example from above to highlight how the introduction paragraph can be written.

Starting at the beginning of the introduction, the first sentence is fairly generic, but related to the title of the article. The second sentence is more specific. It highlights that older adults tend to have larger centre of pressure movements at a higher speed than younger adults. Remember that the title of the article is the effects of balance training on healthy older adults. The third sentence discusses how there is an association between markers of postural control and an increased risk of falls.

The final sentence of the introduction section highlights why balance of older adults is important. This makes the assignment interesting and specific. Note that there is more than one reference (breadth of knowledge).

Summary

  • Your first sentence should introduce the topic and may be quite broad
  • Sentences should follow a logical order: least specific to most specific
  • All sentences must be related to the title of your work and referenced

Recommended literature review structure

The following figure shows how you can easily structure your literature review. Make sure that you have an introduction which follows the guidelines above. Your main body is likely to have two or three key areas. For example, you want to look at the effects of cryotherapy on reducing the effects of exercise induced muscle damage (EIMD).

 

Your first paragraph may highlight that EIMD is common in sports or activities which have a high level of eccentric muscle contractions, especially if unaccustomed. You may then define what EIMD is and give references to support your work. It is likely that you would introduce methods to reduce EIMD, including cryotherapy. Finally, you may report that there are a number of ways to administer cryotherapy e.g. crushed ice, ice spray, cold water immersion etc.

The three ways of administering cryotherapy could now form your three areas within the main body. Make sure that you use headings to signpost the reader. For each of the areas, you need to present a range of literature and critically appraise the work.

Discussion (Main body)

In order to formulate a coherent and academically sound review of the literature, it is recommended that you take some time to familiarise yourself with University of Manchester Academic Phrasebank (Click here). This phrasebank should help you to communicate what you have read in a more academic way and be able to compare and contrast a number of studies.

Using our example of cryotherapy for the treatment of EIMD, the main body will consist of three headings: (1) crushed ice; (2) ice spray; (3) cold water immersion. For each of these sections, you will need a number of articles to discuss. Remember, you are not just summarising what others have published; you are to interpret the findings in the context of your perspective (Hall and Getchell, 2014). Practically, this means identifying key aspects of studies, comparing them and attempting to explain results and conclusions.

Using the phrasebank, you should be able to formulate introductory sentences and within sentences which compare and contrast specific areas of the articles (Click here).

Conclusion

This section is used to summarise the key points that you have detailed in the main body of your work.  It is normally limited to one paragraph and reinforces the take home message (Hall and Getchell, 2014). The conclusion often works in the opposite direction to the introduction. That is, to start with the specific points and move to more general statements. Try and use these three points to help you:

  1. Summarising the scope of the review i.e. review cryotherapy in relation to EIMD
  2. Confirmation of hypothesis or research question i.e. is cryotherapy useful to reduce the effects of EIMD within a sporting population
  3. Finish with a more general statement about how the topic relates to its context. You may also give areas for future research e.g. the duration of ice application

Q1. The introduction should give clear definitions of basic concepts

  • True
  • False

Q2. Your introduction should contain references

  • False
  • True

Q3. A broad knowledge base is shown by

  • What you have read
  • Analysis of what you have read

Q4. Sentences should follow a logical order

  • True
  • False

Q5. Your review should just

  • Summarise what others have written
  • Attempt to interpret the findings in context of your perspective

Q6. Each paragraph should contain (tick all that apply)

  • Topic sentence
  • Supporting sentences
  • Conclusion

Q7. The conclusion summarises the key points of your review

  • True
  • False

Q8. How many paragraphs should your conclusion normally be?

  • One
  • Two
  • Three

Q9. Your conclusion should reinforce the take home message

  • False
  • True

Statistics

Data analysis 1

Hypothesis testing

Moving from a hypothesis to making inference is undertaken by a process known as hypothesis testing (Hall & Getchell, 2014).  This is an objective method to show difference between groups.  For example, you may wish to compare the effects of proprioceptive neuromuscular facilitation (PNF) versus static stretching on hip range of movement.  In this particular study, you would be comparing the range of movement between two groups: PNF and static.  Based upon the results of the study, you may find that one treatment is more effective than another or that there is no difference.
 

Research and alternate hypothesis

Developing an appropriate statistical hypothesis is an important part of the research process (Hall & Getchell, 2014).  These are the hypotheses that prompt the research (Vincent & Weir, 2012).  The hypothesis tested using statistical analysis is usually the null hypothesis.

The null hypothesis predicts that there is no relationship or no difference between groups (Vincent & Weir, 2012).  These two hypotheses are mutually exclusive; if the null hypothesis is true, then the alternate is false.

Using our study above, we can formulate the null and alternate hypotheses.

  1. Null hypothesis: there is no difference between ROM at the hip following PNF or static stretching.
  2. Alternate hypothesis: there is a difference between ROM at the hip following PNF or static stretching.

Accepting or rejecting the null hypothesis

After using the appropriate statistical test, we either accept or reject the null hypothesis.  For example, if we found that there was a significant increase in ROM in the PNF group compared to the static stretching group we would reject the null hypothesis and accept the alternate hypothesis.  Therefore, your conclusions would be that PNF stretching increases ROM at the hip compared to static stretching.

Data analysis 2

Normal distribution

We use normal distribution to show the pattern of distributed data and is an important concept in statistics (Williams & Wragg, 2006).  Williams and Wragg (2006) highlight two important reasons for the importance in statistics:

  1. Normal distribution occurs naturally in many types of data
  2. Many statistical tests assume that the data is normally distributed (use of parametric statistical tests)

What does normal distribution look like for a given set of data?
 

Figure 2.1. The normal curve (Hall & Getchel, 2014)

Figure 2.1 shows what a normal distribution curve looks like. This curve is a frequency plot of normally distributed scores.  For example, if we measured the body mass of all male sports therapy students at UCB, their data would most likely fit under the curve. There would be some people on the left hand side (short), the majority would be around the middle (mean) and others on the right hand side (tall). The shape of this curve is known as the bell curve.

Standard deviation

The standard deviation is used to indicate the variability of the distribution within a data set (Hall & Gretchell).  Specifically, the standard deviation estimates the spread of the scores away from the mean. Figure 2.1 shows the mean of a given data set and the associated standard deviations. In most published work, data is expressed as the mean ± 1 standard deviation.  This accounts for approximately 68% of all of the scores.

The following tutorial shows you how to calculate the standard deviation using Excel (www.statisticshowto.com).

Test for difference

Now that you have learnt how to test for normality of data and calculate the mean and standard deviation, you can now start to look at specific statistical tests.

Our first test is the t-test. This test is used to test for a difference between two sets of data.  There are two types of t-test: independent and dependent. Both of these tests must satisfy a set of assumptions or the test will be violated.  If this occurs, the test may be invalid. The three assumptions for the t-test are:

  1. Data must be normally distributed
  2. Samples must be randomly selected from a population
  3. The variance of each sample must be approximately equal (homogeneity of variance)

You can use Excel or Minitab to perform this test. Revisit the lecture notes and perform a t-test on the following sets of data.

Table 1. Vertical jump performance (caffeine vs. no caffeine)

Vertical jump (cm)
No caffeine Caffeine
24.2 27.9
25.1 26.8
23.4 29.7
22.9 30.4
24.3 28.7
25 30.2
24.9 27.9
23.8 26.9
23.7 28.4
22.8 29.1
21.6 28.8
24.6 27.8

Did you accept or reject the null hypothesis?  What were the results of your analysis?

Q1. The process of hypothesis testing involves

  • Creating hypotheses
  • Setting probability levels
  • Calculating critical statistical levels
  • Performing the statistical analysis
  • Performing the statistical analysis
  • Making a decision about group differences
  • Making a decision about group differences
  • All of the above

Q2. Hypothesis testing can be used to show differences between groups

  • True
  • False

Q3. The null hypothesis suggests

  • There is no difference between the groups
  • There is a difference between the groups

Q4. If the null hypothesis is rejected, we

  • Accept that there is no difference
  • Accept that there is a difference between the group(s)

Q5. Parametric statistics are usually used with

  • Non-normally distributed data
  • Normally distributed data

Q6. The shape of the curve for normally distributed scores is known as

  • Bell curve
  • J curve
  • Inverted U curve

Q7. The standard deviation is used to measure the variability of the distribution within a data set

  • False
  • True

Q8. Assumptions for a t-test are

  • Normal distribution
  • Randomly selected
  • Variance of each sample must be approximately equal
  • All three

Statistics - correlation

Statistics - correlation

Correlation

A statistical technique used to examine the relationship between or among variables. Basically, it involves quantifying the relationship between two variables. Variables can display positive, negative or no relationship.

Look at the following figure and see if you can remember the direction of the relationship.

Figure 1. Relationships between maximal oxygen uptake and 6 min (A) and 1 min (B) run.

What were your answers?

In the top image, we can see that as maximal oxygen uptake increased (VO2 max), distance covered in 6 minutes also increased (direction went from bottom left to top right). This is known as a positive correlation.

The bottom image also shows an increase in performance. However, based upon the outcome measure, time on the 1 mile run decreases as VO2 max increases. Therefore, this relationship is a negative correlation (top left to bottom right).

Strength of correlation

Now you can (hopefully) identify the direction of the correlation, you need to be able to understand the strength of the correlation. Values for correlation range between -1 and +1. The closer the value to either of these numbers, the stronger the correlation.

Click on the link to read the following study: Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players (click here)
 

Figure 2. Relationship between 10 m sprint and 1 RM (Wisloff et al., 2004)

The strength of the relationship between 10 m sprint time and 1 RM for the elite football players was 0.94 (r= 0.94). The figure shows that a higher 1 RM correlated with a quicker 10 m sprint time (stronger athletes were faster over 10 m).
 

Figure 3. Relationship between jump height and 1 RM (Wisloff et al., 2004)

Figure 3 shows the relationship between vertical jump height and 1 RM for elite football players. Based upon the direction of the slope, an increase in 1 RM is correlated with an increase in jump height (stronger athletes could jump higher). The strength of correlation is 0.78 and this may be seem as moderate.

Question

From the data presented in Figures 2 and 3, which showed the strongest correlation?

Q1. A method to examine the relationship between or among variables is known as

  • Analysis of variance
  • Correlation
  • Coefficient of variation

Q2. If the data plot goes from bottom left to top right, the correlation is said to be

  • Negative
  • Positive

Q3. The data plot of a negative correlation would be

  • Top left to bottom right
  • Bottom left to top right

Q4. 0.75 is a stronger relationship than -0.76

  • True
  • False

Q5. A correlation of 0.78 is said to be

  • Strong
  • Moderate
  • Small