Chapter 3

Using the empirical rule, what percent of observations are more than two standard deviations from the mean in either direction?

5%

If a data distribution is mound shaped and approximately symmetric, then approximately what percent of observations are within one standard deviation of the mean?

68%

Using the empirical rule, what percent of observations are below a value corresponding to one standard deviation above the mean?

84%

If a data distribution is mound shaped and approximately symmetric, then approximately what percent of observations are within two standard deviations of the mean?

95%

If a data distribution is mound shaped approximately symmetric, then approximately what percent of observations are within three standard deviations of the mean?

99.7%

Which of the following is not included in the five-number summary?

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A _____ is a compact display that provides information about the center, variability, and symmetry or skewness of a data distribution.

Boxplot

Measures of _____ describe where the data distribution is located along the number line.

Center

In a boxplot, which of the following symbols would denote an outlier?

Dot

Large deviations from the mean signify small variability among the data.

False

The main deficiency of the sample mean is that it is insensitive to outliers.

False

The mean and interquartile range are used to describe the center and spread of a symmetric distribution.

False

The process of subtracting the mean and then dividing by the standard deviation is referred to as deviation.

False

The z-score tells you how many standard deviations the data value is from the minimum.

False

The _____ range is calculated by taking the upper quartile minus the lower quartile.

Interquartile

Which of the following measures is used to describe the variability of a distribution with outliers?

Interquartile range

The sample _____ is the arithmetic average of the values in a sample.

Mean

Which of the following measures is used to describe the center of a symmetric distribution?

Mean

The lower _____ is the median of the lower half of the data set.

Quartile

The simplest measure of variability is the _____, which is the difference between the largest and smallest observations in the data set.

Range

If a data distribution is mound shaped and approximately symmetric, then the median is approximately equal to the mean.

True

If the sample size is odd, the median of the entire data set is excluded from both halves of the data when calculating quartiles.

True

The interquartile range measures variability by looking at how spread out the middle half of the data is.

True

The quartiles separate the data set into four equal parts or quarters.

True

The sample median is insensitive to outliers because the median use at most two values from the sample to be calculated.

True

The standard deviation is a more commonly used measure of variability than the variance because it has the same units as the original data set.

True

The sum of the deviations from the mean is always equal to zero.

True

The z-score is positive if the data value is greater than the mean.

True

The sample _____ is the sum of the squared deviations from the mean divided by n-1.

Variance