Question

The time to complete a standardized exam in the BYU-Idaho Testing Center is approximately normal with a mean of 70 minutes and a standard deviation of 10 minutes. Using the 68-95-99.7 rule, approximately what percentage of students will complete the exam in under fifty minutes? Give your answer accurate to one decimal place.

Answer 1

Answer:

Step-by-step explanation:

Given that X the time to complete a standardized exam  in the BYU-Idaho Testing Center is approximately normal with a mean of 70 minutes and a standard deviation of 10 minutes.

We have 68 rule as 2/3 of total would lie within 1 std deviation, and 95 rule as nearly 95% lie within 2 std deviations from the mean.

We have std deviation = 10

Hence 2 std deviations from the mean

= Mean ±2 std deviations

=$70$±20

= $(50,90)$

Below 50, 0.25 or 2.5% would complete the exam.