At LLD Records, some of the market research of college students is done during promotions on college campuses, while other market research of college students is done through anonymous mail, phone, internet, and record store questionnaires. In all cases, the company solicits an intent to purchase score from the student, with being the lowest score ( no intent to purchase ) and being the highest score ( full intent to purchase ).
The manager finds the following information for intent to purchase scores for a soon to be released CD:
group sample size sample mean sample variance
on campus 23 68.1 128.5
by mail 23 69.6 94
by phone 23 62.4 84.4
by internet 23 69.4 185.5
in a store 23 63.4 55.3
Suppose that the five populations of scores from which these samples were drawn are approximately normally distributed and have the same mean and the same variance.
Answer the following, carrying your intermediate computations to at least three decimal places and rounding your responses to at least one decimal place.
Give an estimate of this common population variance by pooling the sample variances given.
Give an estimate of this common population variance based on the variance of the sample means given.