33,220 32,290 23,090 24,010 31,830 33,010 30,970 30,120 32,630 32,030 32,660 31,

Question

33,220
32,290
23,090
24,010 31,830
33,010
30,970
30,120 32,630
32,030
32,660
31,320 26,510
30,470
33,600
28,770 33,260
32,730
32,340
31,950 33,220
32,290
23,090
24,010 31,830
33,010
30,970
30,120 32,630
32,030
32,660
31,320 26,510
30,470
33,600
28,770 33,260
32,730
32,340
31,950 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. (a) We are willing to regard the wood pieces prepared for the lab session as an SRS of all similar pieces of Douglas fir. Engineers commonly assume that characteristics of materials vary Normally. Make a graph to show the shape of the distribution for these data. (Do this on paper. Your instructor may ask you to turn in this work.) Does the Normality condition appear safe? Suppose that the strength of pieces of wood like these follows a Normal distribution with standard deviation 2750 pounds. (Select all that apply.)

Explanation / Answer

Prepare histogram and find that this is not normal shape.

The data do not appear to follow a Normal distribution.

b) 90% confidence level we calculate mean and std dev

Total Numbers

20

Mean (Average)

30840.5

Population Standard deviation

2937.384

Confidence interval lower bound = 30840.5-1.68(2937.384)

Upperbound = 30840.5+1.68(2937.384)

Confidence interval = (25905.69, 35775.31)

Frequency 23090 - 24142 2 24142 - 25194 0 25194 - 26246 0 26246 - 27298 1 27298 - 28350 0 28350 - 29402 1 29402 - 30454 1 30454 - 31506 3 31506 - 32558 5 32558 - 33610 7

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