200 students took the final,15 of them are repeating the class.the mean of the s

Question

200 students took the final,15 of them are repeating the class.the mean of the scores is 70 and the standard deviation is 10 (a)what percent of the scores do you expect to lie between the values 65 and 85? (b)what percent of the scores do you expect to lie between the values 55 and 95? (c)what percentage of students are repeating the class? 200 students took the final,15 of them are repeating the class.the mean of the scores is 70 and the standard deviation is 10 (a)what percent of the scores do you expect to lie between the values 65 and 85? (b)what percent of the scores do you expect to lie between the values 55 and 95? (c)what percentage of students are repeating the class? (a)what percent of the scores do you expect to lie between the values 65 and 85? (b)what percent of the scores do you expect to lie between the values 55 and 95? (c)what percentage of students are repeating the class?

Explanation / Answer

a) P(65<x<85)

=P((65-70)/10<z<(85-70)/10)

=P(-0.5<z<1.5)

= 0.6247

b) P(55<x<95)

= P((55-70)/10<z<(95-70)/10)

= P(-1.5<z<2.5)

= 0.9270

c) percentage of students are repeating the class = 15/200

= 7.5%

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