#9 a) = 0.5, = 0.768 b) = 0.76, = 0.341 c) = 0.76, = 0.012 d) = 0.5, = 0.5 a) = 0.37, = 0.63 b) = 0.5, = 0.37 c) = 0.37, = 0.63 d) = 0.37, = 0.043 3. The advertising department of a nationally circulated magazine wishes to estimate the mean age of its subscribers to within year with 90% confidence. If they estimate that the standard deviation of the ages of their subscribers is about 5 years, what is the minimum size of the sample they must take? a) 17 4. 5. 6. b) 165 c) 45 d) 271 e) 13