Question

A computer software company would like to estimate how long it will take a beginner to become proficient at creating a graph using their new spreadsheet package. Past experience has indicated that the time required for a beginning to become profiencent with a particular function of the new software product has an approximately normal distribution with a standard deviation of 19 minutes.

Find the minimum sample size necessary to estimate the true average time required for a beginner to become proficient at creating a graph with the new spreadsheet package to within 8 minutes with 80% confidence.

Answer 1

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Answer:

Given that,

standard deviation =s =   =19

Margin of error = E = 8

At 80% confidence level the z is ,

= 1 - 80% = 1 - 0.80 = 0.20

/ 2 = 0.20 / 2 = 0.1

Z/2 = Z0.1 = 1.28

sample size = n = [Z/2* / E] 2

n = ( 1.28*19 /8 )2

n =9.2416

Sample size = n ~10