An advertising agency is interested in developing a new television advertising for one of its clients who produces toys for children.The agency is interested in conducting its own survey on the amount of hours children watch television during the week. Previous related research indicated a population standard deviation (σ) of 80 minutes. If the agency uses a confidence level of 95%, how large a sample should they use? The agency indicated that the range of the interval should be within 15 minutes.
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Formula for determining population sample:
ReplyDeleten= (z*standard deviation of pop./m)^2
therefore, a 95% confidence corresponds to a z-value of 1.960.
the marginal error can be found by dividing 15/2=7.5
n = (1.96*80/7.5)^2
= 437.09
n = 438 people