An automobile insurance firm wants to find the average amount per claim for auto body repairs. Its summary records combine amounts for body repair with all other amounts, so a sample of individual claims 'must be taken. A similar study done in the previous year shows that the standard deviation is about $400.
A 90% confidence interval with a width no greater than $50 (i.e., margin of error = $25) is wanted. How large a sample is need? Your answer should be an integer.
A 95% confidence interval with a width no greater than $50 (i.e., margin of error = $25) is wanted. How large a sample is need? Your answer should be an integer.
Does your sample size in parts a, b, and c increase as the confidence level C increases?