Computers Magazine has recently completed an analysis of itscustomer base. It has determined that 75% of the issues sold eachmonth are subscriptions and the other 25% are sold at newsstands.It has also determined that the ages of its subscribers arenormally distributed with a mean of 44.5 and a standard deviationof 7.42 years, whereas the ages of its newsstand customers arenormally distributed with a mean of 36.1 and a standard deviationof 8.20 years.
(a) Computers Magazine would like to make the followingstatement to its advertisers: “80% of our subscribers are betweenthe ages of . . . and . . . .” Your job is to fill in the blanks,choosing a range that is symmetric around the mean. (In otherwords, the mean age of subscribers should be the midpoint of therange.)
(b) What proportion of Computers Magazine newsstand customershave ages in the range you gave in (a)?
(c) What proportion of all of Computers Magazine customers haveages in the range you gave in (a)?
