Question

5. A manufacturer of college textbooks is interested in estimating the strength of the bindings produced by a particular binding machine. Strength can be measured by recording the force required to pull the pages from the binding. If this force is measured in pounds, how many books should be tested in order to estimate with 95% confidence to within 0.1 lb the average force required to break the binding? Assume that  is known to be .8 lb.

6. We want to estimate, with a maximum error of .02, the true proportion of all senior medical students who plan to specialize in internal medicine, and we want 90% confidence in our results. What size sample is necessary?

Answer 1

Solution :

5) Z/2 = Z0.025 = 1.96  

sample size = n = [Z/2* / E] 2

n = [ 1.96 * 0.8 / 0.1 ]2

n = 245.86

Sample size = n = 246

Solution,

Given that,

6)  Z/2 = Z0.05 = 1.645

sample size = n = (Z / 2 / E )2 * * (1 - )

= (1.645 / 0.02)2 * 0.5 * 0.5

= 1691.27

sample size = n = 1692