Question

The scores on a final exam were approximately normally distributed with a mean of 82 and a standard deviation of 11. If 85 students took the exam, and above a 60 is a passing grade, how many students failed the exam?

Answer 1

2 students failed the exam

Explanation:

Answer 2

In this case, we can use the z statistic to find for the proportion of students who failed the exam. The formula for z score is given as:

t = (x – u) / s

where,

x = the sample score = 60

u = sample score mean = 82

s = standard deviation = 11

Substituting all given values into the equation:

t = (60 – 82) / 11

t = - 2

Based from the standard proportion distribution tables for z, this corresponds to:

P = 0.0228

This means that 2.28% of the students failed the exam or equivalent to:

failed students = (0.0228) * 85 = 1.938

approximately 2 students failed the exam