A researcher records the sound (in decibels)during a series of lessons taught by a substitute teacher at a local elementary school.In his study,he found that the sound was 80 ± 6 (M ± SD)decibels.Assuming the data are normally distributed,which of the following is an appropriate conclusion?
A) At least 68% of classes were between 76 and 84 decibels.
B) At least 5% of classes were louder than 68 decibels.
C) At least 95% of classes were between 68 and 92 decibels.
D) All of these.

Question

Quizplus · Accepted Answer

In a normal distribution, approximately 95% of the data falls within two standard deviations from the mean. Here, the mean is 80 decibels and the standard deviation is 6 decibels, so 68 to 92 decibels covers this range.

A Researcher Records the Sound (In Decibels)during a Series of Lessons