Problem 7.013 a random sample of size n1 = 16 is selected from a normal population with a mean of 73 and a standard deviation of 9. a second random sample of size n2 = 8 is taken from another normal population with mean 70 and standard deviation 11. let upper x overscript bar endscripts subscript 1and upper x overscript bar endscripts subscript 2 be the two sample means. find: (a) the probability that upper x overscript bar endscripts subscript 1 baseline minus upper x overscript bar endscripts subscript 2 exceeds 3. (b) the probability that 4.9 less-than-or-equal-to upper x overscript bar endscripts subscript 1 baseline minus upper x overscript bar endscripts subscript 2 baseline less-than-or-equal-to 5.7.

An annual marathon covers a route that has a distance of approximately 26 miles. winning times for this marathon are all over 2 hours. the following data are the minutes over 2 hours for the winning male runners over two periods of 20 years each. earlier period 14 12 15 22 13 10 19 13 9 14 20 18 16 20 23 12 18 17 6 13 recent period 7 11 7 14 8 9 11 14 8 7 9 8 7 9 9 9 9 8 10 8 (a) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the earlier period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks. for more details, view how to split a stem.) minutes beyond 2 hours earlier period 0 1 2 (b) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the recent period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks.) minutes beyond 2 hours recent period (c) compare the two distributions. how many times under 15 minutes are in each distribution