Billie wishes to test the hypothesis that overweight individuals tend to eat faster than normal weight individuals. To test this hypothesis, she has two assistants sit in McDonald’s restaurants and identify individuals who order at lunch time the Big Mac special (Big Mac, large fries, and large coke). The Big Mackers, as the assistants affectionately called them, were classified by the assistants as overweight, or neither nor normal weight. The assistants identify 10 overweight Big Mackers and 30 normal weight Big Mackers. (individuals who were neither overweight nor normal weight were disregarded).
The assistants record the amount of time it took for the individuals in the two groups to complete their BIG Mac specials meals. One variable is weight with two levels, Overweight (=1) and normal weight (=2). The second variable is time in seconds.
1. Compute a Mann-Whitney U test on these data. From the output, identify the following:
A: p value
B: z value corrected for ties
C: Mean rank for normal weight individuals
2. Conduct an independent-samples T test. Compare the p value for the Mann-Whitney U test with the p value for the independent samples test
3. Write a results section based on your analyses. What should you conclude?
4. If you did not include a graph in your results section, create a graph that shows the distribution of the two groups.