Presidents also take midterms! After two years of the president's term, members of Congress are up for

Question:

Presidents also take midterms! After two years of the president's term, members of Congress are up for election. The following table gives the number of net seats lost, by the party of the president, in the House of Representatives starting from Eisenhower's time.
Net House Seats Lost in Midterm Elections

For the data on the number of House seats lost:
(a) Calculate the sample mean.
(b) Calculate the standard deviation.
(c) Make a dot plot.
(d) What is one striking feature of these data that could be useful in predicting future midterm election results? (Would you have expected more elections to result in net gains?)