A study was conducted to assess the effectiveness of a health promotion program to improve the level of fitness of children aged 5-9 years. The fitness of 25 children who participated in the study was determined by measuring the total distance each child could run in a 9-minute period. The researchers calculated the difference in the distance (in metres) ran before the health promotion program commenced and after it was completed (i.e. the distance ran after the program minus the distance ran before the program).

a) What are the study factor and the primary outcome factor?

b) State the null and alternative hypotheses of the study.

c) Which of the two statistical tests shown in the Appendix (pages 3-6) would be appropriate to evaluate the hypotheses you have stated in Question 1(b)? Explain the reasons for your decision based on the information provided in the Appendix.

d) Interpret the result of the test you have chosen in 1(b).

e) Write a brief conclusion about the results of the study.

f) Considering the design of this epidemiological study:

i. What is the best feasible type of study to determine whether the health promotion program was associated with a change in children's fitness? Provide reasons for your answer.

ii. If the researchers used the study design you recommended in Q1fi, what advice would you give them about selectingthe study participants to minimise selection bias?

iii. What advice would you give to the researchers about how to avoid measurement error when assessing the outcome factor if they used the study design you recommended in Q1fi?