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
=±20
=
Below 50, 0.25 or 2.5% would complete the exam.