How heavy a load (pounds) is needed to pull apart pieces of Douglas fir 4 inches

Question

How heavy a load (pounds) is needed to pull apart pieces of Douglas fir 4 inches long and 1.5 inches square? Here are data from students doing a laboratory exercise:       

We are willing to regard the wood pieces prepared for the lab session as an SRS of all similar pieces of Douglas fir. Suppose that the strength of pieces of wood like these follows a Normal distribution with standard deviation 3200 pounds.

Give a 90% confidence interval for the mean load required to pull the wood apart (give your answer with three decimal places).

The sample mean is ________  (give three decimal places)

90% confidence interval for the mean load is ____________ to ________ .

PLEASE MAKE SURE YOUR ANSWER IS CORRECT AND PROVIDE FILL IN THE BLANK     

25071 30000 32703 27865 29482 25660 30540 34676 28285 29968 26179 27838 22154 28710 24569 31942 26148 31122 27101 28683

Explanation / Answer

here sample mean =total/20=28434.8

also std error =std deviation/(n)1/2 =715.542

for 90% CI, z=1.645

hence confidence interval =sample mean -/+z*std error =27257.839 ; 29611.761

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