A sales manager wishes to predict sales based on the dollar value of quotes made by the sales staff. She collects data on the total dollar value of quotes given to prospective clients and also records the dollar volume of sales in each month over the past year. The data are shown in the file "exercise3.xls".
a. Plot a scatter diagram for Sales volume vs. Quotes volume. Insert the trend line in the scatter plot. Calculate the correlation coefficient between sales volume and quotes volume.
b. Plot a scatter diagram for Sales volume (t) vs. Quotes volume (t-1). Calculate the correlation coefficient between sales volume(t) and quotes volume(t-1).
Hint: Question 1b deals with the relationship between sales in a particular month (t) and the quote in the month before that (t-1).
Grades of two courses for the same 500 students are listed in file "lecture1.xls". Perform a t-test, and plot the means and standard errors in a bar graph.