6. A manufacturer wishes to estimate the mean dimension of a certain component. He would be satised if he obtained an estimate within 0.01 cm margin of error of the true mean, and was 95% condent of his result. An initial sample has a standard deviation of 0.2 cm. What sample size should be examined? 7. You want to have 90% condence of estimating the proportion of ofce workers who respond to email within an hour to within :E 0.05. Determine the sample size needed. 8. The telephone company wants to estimate the proportion of households that would purchase an additional telephone line if it were made available at a substantially reduced installation cost. A random sample of 500 households is selected and the results indicate that 135 of the households would purchase the additional telephone line at a reduced installation cost. Construct a 99% condence interval estimate for the population proportion of households that would purchase the additional telephone line