People applying to a Computing college are given an aptitude test. Those who are accepted take a progress test 3 months after the course has begun. The following table gives the aptitude test scores, x, and the progress test scores, y, for a random sample of eight students, A to H.

a. Find the interquartile range of these aptitude test scores.

b. Use the summary totals ­Σx = 588, Σ­x² = 44080, Σ­y = 544 and Σ­y² = 38030 to calculate the variance of the aptitude and progress test scores when they are considered together.

c. The mean progress score for all the students at the college is 70 and the variance is 112. Any student who scores less than 1.5 standard deviations below the mean is sent a letter advising that improvement is needed. Which of the students A to H should the letter be sent to?

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B D F G H. 61 80 ve 74 60 83 92 71 67 53 77 61 70 81 54 63 85