Question

A test of Mathematics skills test is normally distributed with a mean of 90 and a standard deviation of 13. A student receives a score of 101 on the exam. 1) What percent of students did she do better than? 2) What percent of students did she do worse than?

1.

a).8462

b).1977

c).1538

d).8023

2.

a)15.38%

b)55.96%

c)44.04%

d)65.28%

Answer 1

This is a normal distribution question with

P(x < 101.0)=?

The z-score at x = 101.0 is,

z = 0.8462

This implies that

P(x < 101.0) = P(z < 0.8462) = {0.8023} = 80.23%

Option D is correct

PS: you have to refer z score table to find the final probabilities.

b)

P(worst than) =P(X>101)

P(x>101)=1-P(x<101)=1-0.8023 = 0.1977= 19.77%

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