A civil engineer is analyzing the compressive strength of concrete. Compressive strength is normally distributed with σ² = 1000(psi)². A random sample of 12 specimens has a mean compressive strength ofx¯=3250psi
Construct a 95% two sided confidence interval on mean compressive strength.

confidence intervals (3232.10 , 3267.89)

Step-by-step explanation:

Explanation:-

Confidence intervals on mean :-

The values χ ± 1.96 б/  is called the 95% of confidence intervals  

Given sample size 'n' = 12

mean value 'x' = 3250

and variance σ² = 1000

now standard deviation σ =

now the confidence interval ( χ - 1.96 б/ ,  χ + 1.96 б/ )

substitute given values and simplification , we get

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95 % of confidence intervals are (3232.10 , (3267.89)

The given mean value is lies between in these confidence intervals

(3232.10 , (3267.89)

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