The survey conducted for .

According to survey the average noise is .

The standard deviation is .

**(a) **A normal conversation is held at about .

Find the number of hours during the study that the noise level was this low.

is from the mean.

Because of the data values with in two standard deviations from the mean, each tail represents of the data.

The area to right of is .

.

The number of hours during the study that the noise level was this low is .

(b)

Find the percent of the study during which the noise was between and .

The percent of the study during which the noise was between and is represented by and .

From emperical rule:

The total area under the curve between to is

The percent of the study during which the noise was between and is .

(a) The number of hours during the study that the noise level was this low is .

(b) The percent of the study during which the noise was between and is .

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