Basic Marketing Research with Excel 3rd Edition by Alvin Burns,Ronald Bush

Exercise 14

We have a 7-point scale to measure the construct: likelihood of buying a new car. We wish to estimate the mean score on the scale and we want to be 95% confident that our sample statistic (mean) is within ± 0.5 of a scale point from the true population parameter.
a. Calculate the required sample size.
b. After you calculate the sample size in 27a, you decide you want to halve the level of accuracy.
What would the new sample size be?