Question

Math scores on the SAT exam are normally distributed with a mean of 514 and a standard deviation of 118. If a recent test-taker is selected at random, what is the probability the student scored 691 or greater on the exam ?

Answer 1

The probability is 0.06681

Explanation:

To calculate this, we need to calculate the standard score or z-score

Mathematically, the standard score can be calculated using the formula;

z-score = (x - mean)/SD

from the question, the mean is 514 and the standard deviation is 118

The z-score is thus = (691-514)/118 = 177/118 = 1.5

The probability we are trying to calculate is thus;

P(x ≥ 691) or P(z ≥ 1.5)

Using standard score table or calculator,

Recall, P( x < 691) = 1 - P( x ≥ 691)

Hence, P( x ≥ 691) = 1 - P( x < 691)

P( x ≥ 691) = 1 - 0.93319

= 0.06681