Chapter 10 Assignment 10-5. Using the formula provided in your text, determine the approximate sample sizes for each of the following cases, all with precision (allowable error) of ±5%: Variability of 30%, confidence level of 95% Variability of 60%, confidence level of 99% Unknown variability, confidence level of 95% Please show your calculation to earn full credits. 10-15. The following items pertain to determining sample size when a mean is involved. Calculate the sample size for each case. Please show your calculation to earn full credits. Case Key Variable A B C D Standard Deviation Acceptable Error Confidence Level Number of car rentals per year for business trip usage 10 2 95% Number of songs downloaded with iTunes per month 20 2 95% Number of miles driven per year to commute to work 500 50 99% Use of a 9-point scale measuring satisfaction with the brand 2 0.3 95% Sample size