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If the manager of a paint supply store wants to​ estimate, with 90​% confidence, the mean amount of paint in a​ 1-gallon can to within plus or minus ±0.005 gallons and also assumes that the standard deviation is 0.048 gallons, what sample size is​ needed?

Answer 1

Solution:

The sample size formula is given as below:

n = (Z*σ/E)^2

We are given

Confidence level = 90%

So, critical Z value = 1.6449

(by using z-table)

σ = 0.048

E = 0.005

n = (1.6449*0.048/0.005)^2

n = 249.3569

Required sample size = 250