Distribution question help

lilyungn

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Jun 20, 2010
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Hi all I'm currently taking Statistics 1 and I'm stuck on a homework problem that I've been trying to figure out for a while...hopefully one of you guys can enlighten me on how to do it..heres the question:

The following data represent the scores of a sample of 50 students on a statistics exam. The mean score is x bar = 80.3 and the standard deviation is s = 11.37.

49 51 59 63 66 68 68 69 70 71
71 71 73 74 76 76 76 77 78 79
79 79 79 80 80 82 83 83 83 85
85 86 86 88 88 88 88 89 89 89
90 91 92 92 93 95 96 97 97 98

What percentage of the scores fall in each of the intervals ± s, ± 2s, and ± 3s? Based on these percentages, do you believe that the distribution of scores is approximately normal? Explain.

Any help will be greatly appreciated. Thanks
 
The mean is 80.3 and the SD is 11.37.

To find which fall within one SD, the score must fall in the range 80.3-11.37=68.93 to 80.3+11.37=91.67

For 2 SD, the score must fall in the range 80.3-2(11.37)=57.56 to 80.3+2(11.37)=103.04

The same technique for 3 SD's. That's all there is to it.
 
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