Reference no: EM132657233 , Length: 1122 Words

Part A

Researchers are interested in the health benefits of participating in Veganuary, the pledge for people to adopt a Vegan diet for the month of January. From a convenience sample of 120 adults they randomly allocate half into a Veganuary intervention group and half into a "diet-as-is" group (i.e. nothing changes). The height, age, and gender of each participant was recorded and then their weight was measured at two time points: 1st December (Baseline) and 1st February (Post-Intervention) and a difference value (Diff BMI) was calculated to assess weight loss. Their weight was used to calculate their Body Mass Index (BMI; = Weight/Height2), a normalised measure of whether a person's weight is healthy (<25) or obese (>30). Participants were further divided into three groups, participants that at baseline had a low, medium or high BMI. The researchers predicted that the vegan diet would lead to a decrease in BMI relative to the "diet-as-is" group, particularly so, for participants with high BMI.

The output of the analysis is presented in Tables B1a-b below. ‘Group' refers to which diet group participants were in (Veganuary, Diet-As-Is), and Original BMI refers to participants allocation to a BMI group at the baseline timepoint (Low, Medium and High).

1) What type of ANOVA should be conducted on these data and why?
2) How many factors are there and how many levels does each have? Please provide a description of the levels in each factor.
3) Is there any cause for concern in the Levene's and in case of follow up comparisons which post hoc correction should be applied?
4) Report the main effects and interactions using the traditional notation and describe if they are significant or not
5) What do these tests tell us about whether the intervention may be influencing participant BMI?
6) Using the means displayed in Table B1a, identify which of the four plots below correctly represents the data. Using the graph, explain what is likely to be driving the effects reported in (4).

7) What do the pairwise comparisons for Group displayed in Tables 2g tell us (provide the statistical evidence)?
8) Explain three issues and potential improvements that may be made to the study

Part B

A team of researchers was interested in understanding how children's mathematical abilities changed with age. To analyse this question they recruited 7, 9 and 11 years old children, and asked them to do a mathematical quiz. Researchers collected participants accuracy's on the quiz in percentage.

1. Using the traditional notation, report whether the analysis presented in table C1 indicates if there was a significant main effect of Age Groups and what the shape of the effect was, i.e. the trend.

2. Which graph below corresponds to participants results and why?

3. Based on table C1 and selected graph should the researchers conclude that children change their mathematical abilities linearly with age?