急 ! F5 about Dispersion 13q5

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2013-03-21 3:27 am

請詳細步驟教我計以下二條 : 6. In a public examination, the standardscore of Wilson is -3.0. suppose the scores in the examination are normallydistributed and there are 20000 candidates in the examination.(a) Find the percentage of candidates withscores higher than Wilson.(b) Find the number of candidates withscores higher than Wilson. 11. In a bowling competition, Mandy scores125 and her standard score is -1.7 while Tracy scores 203and her standard score is 2.2(a) Find the mean and the standarddeviation of the scores in the competition.(b) If Maggie scores 170, find her standardscore.

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用戶30507

2013-03-22 1:42 am

✔ 最佳答案

6(a)
From standard normal distribution table, P(Z<3)=0.4978
Thus the percentage of candidates with scores higher than -3 is
0.5+0.4978=99.78%

6(b)
number of candidates performed better than Wilson=20000x99.78%=19956

11. (a)
Let the mean be x and standard deviation be s.
From Mandy, (125-x)/s=-1.7
From Tracy, (203-x)/s=2.2
Solving, s=20, x=159

11.(b)
Maggie's standard score=(170-159)/20=0.55

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