Acivil engineer is analyzing the compressive strength of concrete. compressive strength is approximately normally distributed with variance σ2 = 800 psi2. it is desired to estimate the compressive strength with an error that is less than 13 psi at 95% confidence. what sample size is required? round your answer up to the nearest whole number. the answer must be exact.

19

Explanation:

The minimum sample size is given by

hence making n the subject

Standard deviation, hence

Significance level, =1-Confidence=1-0.95=0.05

Critical value= and from z table the critical value is 1.96

The minimum n has to be an integer hence we round it off to the nearest whole number

answer:

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explanation: