1.4 Exercises
These questions will form part of this topic's computer lab.
Exercise 1.1 A research article (Duncan et al. 2018) examined the accuracy of step counts recorded on iPhones. The paper records this information about the selection of participants:
Participants were recruited through word of mouth and posters displayed around the [researcher's] university. Participants were eligible if they were ambulatory, \(\ge 18\) years of age, and owned an iPhone 6 [...] or newer model.
Although 33 participants were selected, the authors note some parts of the study used a smaller sample size because:
... one [subject] lost their phone during the observation period, [and] the other opted out of the [...] test due to personal circumstances.
The paper notes that previous studies have been able to:
[...] demonstrate the accuracy of the iPhone pedometer function in laboratory test conditions. However, no studies have attempted to evaluate evidence [...] in the field.
- What is the issue that the authors raise with previous studies?
- Why did the authors discuss the changes in sample size for some parts of the study?
- How would you describe the sampling method?
- What would you call the information about given about the subjects needing to be ambulatory and 18 years of age or over?
- Among many other things, the researchers compared the mean diference between the number of step counts recorded by manually counting steps and the iPhone-recorded number of steps. What type of test would be appropriate?
- While walking at 2.5 km/h,
the above test produced a \(p\)-value of 0.006.
What does this mean? - The sample size for the part of the study mentioned above was \(n=32\). Do you think the test will be statistically valid?
Exercise 1.2 One study of hearing loss among Iranian students (Mohammadpoorasl et al. 2018) used a cross-sectional study to explore the relationship between hearing loss and headphone use. The article states that
... 890 students were randomly selected from five schools at QUMS (Medicine, Dentistry, Nursing and Midwifery, Public Health, and Paramedical Sciences schools) using a proportional cluster sampling method...
The participants completed a hearing test and completed a Hearing Loss Questionnaire (values are between 17 and 34: higher scores indicating more severe hearing loss).
- What is the population?
- Critique the sampling method: What is the implication for interpreting the results of the study?
- Some of the results are presented in Table 1.1. What statistical test do you think was used to compare the scores for males and females?
- What are the hypotheses being tested about 'Frequency of use'?
| Criterion | Levels | Sample size | Mean | Std. dev | P-value |
|---|---|---|---|---|---|
| Sex | Female | 543 | 19.37 | 2.91 | 0.009 |
| Male | 302 | 19.99 | 3.51 | ||
| Frequency of use | 0, 1 times/day | 194 | 19.2 | 2.87 | 0.001 |
| 2 to 3 times/day | 319 | 19.6 | 2.66 | ||
| More than 3 times/day | 278 | 20.2 | 3.54 | ||
| Earphone use | Yes | 745 | 19.8 | 3.08 | < 0.001 |
| No | 100 | 19 | 1.71 |
Exercise 1.3 In this question, we will consider a paper called Soft Drink Consumption: Do We Know What We Drink and Its Implication on Health? (Martín et al. 2018).
- By doing an internet search, locate the paper. You can read it online and/or download the PDF version.
- After reading the abstract, evaluate the study using the six steps of research discussed in this subject.
- After reading Sections 3.6 (Statistical analysis) and 4 (Results), write down a list of the various statistical techniques and tests that have been used. Which of these have we learnt about so far in this subject?