In Example 7 in Chapter 8 we compared the number of shares of General Electric stock traded on Mondays and on Fridays during February through April of 2011. The trading volumes (rounded to the nearest million) are as follows:
Mondays: 45, 43, 43, 66, 91, 53, 35, 45, 29, 64, 56
Fridays: 43, 41, 45, 46, 61, 56, 80, 40, 48, 49, 50, 41
Using software,
a. Plot the data. Summarize what the plot shows.
b. State the hypotheses and give the P-value for the Wilcoxon test for comparing the two groups with a two-sided alternative hypothesis.
c. Construct a 95% confidence interval for comparing the population medians. Interpret and explain what (if any) effect the day of the week (Monday versus Friday) has on the median number of shares traded.
d. State the assumptions for the methods in parts b and c.