Question

in a normal distribution 31% of the
under 45 and 8% are over 64. If the mean is 50 find the standard deviation

%
50 find the standard deviation​

Answer 1

Answer:

which class

Step-by-step explanation:

do you study

Answer 2

Answer:

Mean = 49.95  & SD = 10

Step-by-step explanation:

z = -0.495  for 31% of the items are under 45

8% of the items are over 64

=> 92% are below 8  

=> z score = 1.405    of items over 64

z score = ( Value - Mean)/SD

=> -0.495 = (45 - Mean) SD

=> -0.495SD = 45 - Mean

=> Mean = 45 + 0.495SD

z score = ( Value - Mean)/SD

=>  1.405 = (64 - Mean) SD

=> 1.405SD = 64 - Mean

=> Mean = 64  - 1.405SD

45 + 0.495SD = 64  - 1.405SD

=> 1.9SD = 19

=> SD = 10

Mean = 64  - 1.405*10  = 49.95

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