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PLEASE HELP ME WITH THIS MATH PROBLEM!!

PLEASE HELP ME WITH THIS MATH PROBLEM!!-example-1

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Explanation:

in general we would need a probabilty table or a probability calculator service on the internet.

but in this case we know.

the man value is 64. and the standard deviation is 6.

so, one standard deviation +/- interval from the mean value is 70 and 58.

and the interval of 2 standard deviations from the mean value is 76 and 52.

and 64 and 76 are exactly the limits we are asked for.

so, remember the normal distribution rule :

68% are within 1 standard deviation.

95% are within 2 standard deviations.

99.7% are within 3 standard deviations.

and 50% are below (and also above) the mean value.

so, we know, 50% of the 350 (= 175) students scored below 64.

95% of the students scored between 76 and 52. as there are 5% left, half of these 5% (= 2.5%) scored even below 52).

so, 95% + 2.5% = 97.5% of the 350 (= 341.25) students scored below 76.

therefore, the number of students that scored between 64 and 76 is

341.25 - 175 = 166.25 ≈ 166

User Jammur
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