Exam 5: Measures of Variability

The university counseling center has treated a large number of students for depression. They find that the standard deviation of depression scores for their pool of students is substantially higher after treatment than before treatment. The most likely explanation is

What happens to the standard deviation when a constant is added to each score? Use the following set of data, and a constant of 2 to illustrate your answer. 1               2               3               4

The difference between s and σ is that σ is

Data points at the extremes of the distribution have

Dispersion refers to

Create a box plot for the above data.

The variance of a sample is typically a larger value than the standard deviation.

The interquartile range is the range of the middle 25% of values.

The population variance is

Create two sets of scores with equal ranges, but different variances.

Data points that lie outside the whiskers in a boxplot are often referred to as

The variance can best be thought of as the

If the whiskers on a boxplot are much longer on the right than on the left, we would suspect that the distribution is

The standard deviation for the numbers 8, 9, and 10 is

Answer the next two questions based on the following box-plot. There no outliers.

What do we mean by an unbiased statistic?

If we know that a set of test scores has a mean of 75 and a standard deviation of 8, we would conclude that

A data set of intelligence scores was collected from high school seniors. The IQ scores ranged from 82 to 113. Which of the following is probably NOT a reasonable estimate of the standard deviation?

Errors that can lead to outliers can occur in

A trimmed sample is one that