Need help with b and c please.

Exercise 4A
Limit your attention to the most “recent” temperature data, (which we define as years 1990-
2013), for New York City. Answer the following questions:
a) For how many years during the recent period, did the annual temperature rise above the
historical mean calculated for the entire period? Does this represent a reasonable, relatively
large or relatively small percentage of the recent years?
b) Of the 25 warmest years in recorded history, what percentage occurs during the recent
period? Do you think the recent period has more or less than its fair share of warmer years?
(Hint: It may help to re-sort the data according to temperature).
c) Is the mean temperature for the recent period higher or lower than that of the entire period?
Calculate the z-score for the recent mean based on the mean and standard deviation for the
entire period. What does the value of the z-score tell you about the difference between the
two means?
d) Draw a Box Plot for the recent years and place it next to the Box Plot obtained from the data
corresponding to the years prior to 1990. Are there any noteworthy differences between the
two?
e) Write a paragraph to summarize your findings: are NYC annual temperatures notably
different in recent times from what they were in the earlier part of the observation period. In
what way?