According to a recent survey, the average earnings in a certain city were $43,80

Question

According to a recent survey, the average earnings in a certain city were $43,800 in Educational Services and $78,500 in the Financial Services industry.

a) Suppose the standard deviation of earnings in Educational Services for the whole of the city was 14,700

and we want the standard deviation of average earnings in our survey to be $1100. What sample size do we need to take?

b) Suppose we used a sample of size 310 for our estimate of average earnings in Financial Services and the standard deviation of earnings in our survey was $19,000. What is the standard error of the average earnings in Financial Services?

Explanation / Answer

here as sample size =(std deviation of population/std deviation of mean)2 =(14700/1100)2 =179

b)

standard error =std deviation of population/(n)1/2 =19000/(310)1/2 =1079.13

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