3. Describing Data Numerically

For a bell-shaped data set, approximately what percentage of the data will be in the interval $\mu -\sigma$ to $\mu +\sigma$?

Which one of the following is the positive square root of the $\mathrm{variance}$?

Significant Values. In Exercises 9–12, use the range rule of thumb to identify (a) the values that are significantly low, (b) the values that are significantly high, and (c) the values that are neither significantly low nor significantly high.

IQ Scores The Wechsler test is used to measure intelligence of adults aged 16 to 80. The mean test score is 100 and the standard deviation is 15.

Exit Velocity Use the frequency distribution whose class width is 4 obtained in Problem 25 in Section 2.2 to approximate the mean and standard deviation exit velocity. Compare these results to the actual mean and standard deviation exit velocity.

In the context of statistics, how can the $s=\sqrt{\frac{\sum {x-\mu }^2}{n}}$ (standard deviation) be used to specify uncertainty in a set of measurements?

From a random sample of airplanes, the number of defects found in their fuselages are listed. Find the sample mean and the sample standard deviation of the data.

According to the range rule of thumb, the standard deviation of a data set can be roughly estimated as which of the following expressions?

Regarding measures of variability, which of the following statistics can take on negative values?

Given a population with mean $\mu$ = $40$ and standard deviation $\sigma$ = $8$, what is the z-score of a value $x=56$?

Which of the following symbols identifies the sample variance?

Which of the following sets of data will have the smallest $standarddeviation$?

If the standard deviation for a set of data is $0$, what does this indicate about the data values?

Which characteristic of data is a measure of the amount that the data values vary?

In a normal distribution, approximately what percentage of data falls below a value that is $3-\sigma$ below the mean $\mu$?

If a set of data has a standard deviation of $0$, which of the following must be true about the data?