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

use calculator

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

The given mean value is lies between in these confidence intervals

(3232.10 , (3267.89)

d. all of the above

step-by-step explanation:

answer: a

step-by-step explanation: the answer is a due to the rule of symmetry; that a line of symmetry must divide a figure into 2 pieces that are the exact same, only reflected over a line of symmetry. b and c do not have lines of symmetry and would not divide the figure evenly, thus making the answer a.