Statistics assignment – Physiology Students Only
{Statistics assignment using SPSS (2000 words equivalent) – 40% }
“Factors Associated with Cycling Time-Trial Performance” A study was recently conducted on a random sample of 30 male cyclists. Skinfold measurements were made using the four-site protocol outlined by Durnin and Womersley (1974). Capillary blood samples were taken at rest to determine haematocrit (Hct) and haemoglobin (Hb) concentration. All cyclists completed an incremental exercise test on a electromagnetically-braked cycle ergometer to determine maximal oxygen uptake (V̇O2max), power output at V̇O2max (Wmax), and power output at the onset of blood lactate accumulation (OBLA; look this up if you aren’t sure what this means). The cyclists completed subsequently a time-trial, on the same cycle ergometer, equal to 25 mins at 85% of Wmax (0.85 × Wmax × 1500). The protocol for the time-trial was the same as that used by Saunders et al. (2017) (pdf in Moodle). The results of the study are presented in Table 1.
Part 1
As principle researcher, you are required to perform an appropriate analysis on these data to respond to the following questions:
1. Construct a table of means and standard deviations using MS Word. Provide a brief commentary on the descriptive statistics (i.e. what do they tell you about the sample – think very carefully about this?).
2. Carry out a preliminary analysis of the relationships between time-trial performance and the explanatory variables. Which explanatory variables do you expect to see in the final model and why? (make sure you include evidence from SPSS to illustrate your conclusions).
3. Select, perform, and discuss the outcome of the best analysis that will tell you which variables are most strongly related to time-trial performance.
4. Using graphs (histogram, residual plot, and P-P plot) to support your answer, comment on the assumptions of the model.
5. Write a 150-word abstract to summarise the findings of the above study.
6. Use the most parsimonious model you developed in part 3 to predict time-trial performance based on the following data from an individual: height 1.67 m; body mass 61.3 kg; body fat percentage 12%; Hct 42%; Hb 16.4 g.dL-1; VO2max 3.8 L.min-1; Wmax 306; OBLA 234 W
7. What are the limitations of the answer to part (6)?
Part 2
In a separate experiment, using a double-blind randomised design, a separate group of male cyclists completed a series of four of the same time-trials as in Part 1, two hours after ingesting different doses of dietary nitrate in the form of concentrated beetroot juice. The four experimental treatments were: placebo, 8.2 mmol nitrate, 16.4 mmol nitrate, and 24.6 mmol nitrate. All time-trials were separated by at least seven days. The results of the experiment are presented in Table 2.
8. Produce a MS Excel graph of these results and briefly comment on any pattern observed. i.e. What do you expect a statistical analysis of these data to show.
9. Using graphs (histogram and Q-Q plot) to support your answer, comment on the suitability of parametric statistics to analyse this data.
10. Select, perform, and report the results of the best analysis that will tell you whether acute beetroot supplementation affects cycling time-trial performance and whether there is a dose-related effect.
11. Write a 150-word abstract to summarise the findings of the above study