Chapter 1. Frequency Distributions: The Big Picture on Depression

1.1 Frequency Distributions: The Big Picture on Depression

Depression can be an isolating condition, but it is also a widespread disorder, affecting 350 million people worldwide. On an individual level, people experience depression differently, but some researchers hoped that looking at depression in a large sample could help clinicians to see its patterns more clearly. A study used the National Survey of Midlife Development (MIDUS) to assess the patterns of depression symptoms in a group of 6223 Americans (Tomitaka et al., 2017). The survey included a standard depression measure, the Kessler Screening Scale for Psychological Distress (K6), which was completed by a representative sample of U.S. adults, ages 25–74. The K6, as its name implies, includes six items that are associated with depression. For each item, survey respondents were asked to indicate how often they felt that way over the past month on a scale of 0 to 4.

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Question 1.1

On the K6, higher numbers contribute to a higher overall depression score. Let’s get a sense of what contributes to a high depression score.

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The six items on the K6 assess how often respondents felt sad, nervous, restless or fidgety, hopeless, worthless, and that everything is an effort. Depressed people often experience a range of symptoms, including those related to anxiety.

1.2

image description

The bar graph shows the score on the K6 generally decreasing as the frequency of feelings increases. The horizontal x-axis is labeled “Score on the K6” and the scores range from “1” to “24.” The vertical y-axis is labeled “Frequency of feelings” and it ranges from “0” to “1800,” in intervals of 300. For a score of “1,” the frequency of feelings is represented by a vertical bar that rises to about 1600; the bar for frequency of feelings drops to about 900 for scores of “2” and “3,” then continues to diminish quickly until the bars for frequency of feelings are below 100 for scores of 12 and higher.

Question 1.2

Participants in the study completed the K6, rating how often they felt each of the six depression-related emotions in the last 30 days. The researchers then summed those scores to create a total score for each participant. Based on the 0–4 scale for each item, the total scores could range from 0 to 24. The graph here shows the histogram for the total scores.

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Correct! There are more scores on the negative end of the x-axis and fewer scores on the positive end of the x-axis, so the graph is positively skewed.

Actually, there are more scores on the negative end of the x-axis and fewer scores on the positive end of the x-axis, so the graph is positively skewed.

1.3

image description

The bar graph shows the score on the K6 generally decreasing as the frequency of feelings increases. The horizontal x-axis is labeled “Score on the K6” and the scores range from “1” to “24.” The vertical y-axis is labeled “Frequency of feelings” and it ranges from “0” to “1800,” in intervals of 300. For a score of “1,” the frequency of feelings is represented by a vertical bar that rises to about 1600; the bar for frequency of feelings drops to about 900 for scores of “2” and “3,” then continues to diminish quickly until the bars for frequency of feelings are below 100 for scores of 12 and higher.

Question 1.3

Here’s the same histogram from the previous screen, which shows the frequency for each total score on the K6.

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Correct! A frequency table shows the frequencies of scores in a data set, but does not show us the overall shape of the distribution.

Actually, a frequency table shows the frequencies of scores in a data set, but does not show us the overall shape of the distribution.

1.4

image description

The bar graph shows the score on the K6 generally decreasing as the frequency of feelings increases. The horizontal x-axis is labeled “Score on the K6” and the scores range from “1” to “24.” The vertical y-axis is labeled “Frequency of feelings” and it ranges from “0” to “1800,” in intervals of 300. For a score of “1,” the frequency of feelings is represented by a vertical bar that rises to about 1600; the bar for frequency of feelings drops to about 900 for scores of “2” and “3,” then continues to diminish quickly until the bars for frequency of feelings are below 100 for scores of 12 and higher.

Question 1.4

Another option for displaying data is a grouped frequency table, which uses intervals to show data within certain ranges. This is helpful for large data sets or for scores with decimal places.

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Correct! With an interval of five, we would be able to see the overall trend of the distribution of data, but might not see more subtle differences.

Actually, with an interval of five, we would be able to see the overall trend in the distribution of data, but might not see more subtle differences.

1.5

image description

The bar graph shows the score on the K6 generally decreasing as the frequency of feelings increases. The horizontal x-axis is labeled “Score on the K6” and the scores range from “1” to “24.” The vertical y-axis is labeled “Frequency of feelings” and it ranges from “0” to “1800,” in intervals of 300. For a score of “1,” the frequency of feelings is represented by a vertical bar that rises to about 1600; the bar for frequency of feelings drops to about 900 for scores of “2” and “3,” then continues to diminish quickly until the bars for frequency of feelings are below 100 for scores of 12 and higher.

Question 1.5

As we noted previously, these data are positively skewed.

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Correct! The lowest possible score is 0, and many participants had a score of 0, creating a floor effect.

Actually, the lowest possible score is 0, and many participants had a score of 0, creating a floor effect.

1.6

1.7

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