Question

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

33,190	31,860	32,590	26,520	33,280
32,320	33,020	32,030	30,460	32,700
23,040	30,930	32,720	33,650	32,340
24,050	30,170	31,300	28,730	31,920

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We are willing to regard the wood pieces prepared for the lab session as an SRS of all similar pieces of Douglas fir. Engineers also commonly assume that characteristics of materials vary Normally. Suppose that the strength of pieces of wood like these follows a Normal distribution with standard deviation 3000 pounds.

PLAN: We will estimate μ by giving a 95% confidence interval.

SOLVE: Find the sample mean ¯x . (Enter your answer rounded to the nearest whole number.)

¯x=

Give a 95% confidence interval, [low,high] , for the mean load required to pull the wood apart. (Enter your answers rounded to the nearest whole number.)

Answer 1