Measures of Variability in Research Psychology

The range, which indicates the fundamental spread of scores; variance; and standard deviation, which reflects the normal spread within the scores, are three popular and widely used measures of variability. The interquartile range, which is the range of the middle half of a distribution, is another measure of variability. Variability shows us how effectively we can generalize the results of the sample to our population. Thus, it is critical. High and low variability are the two types of variability. Because the numbers are less constant here, high variability indicates that making assumptions is more difficult. At the same time, the low variability indicates that we may make better assumptions about the population based on sample data.

What are Measures of Variability?

How far apart the points lie from each other and the center of a distribution or a data set can be known with the help of measures of variability. It can also be referred to as dispersion, scatter or spread. There is a basic difference between central tendency and variability. The central tendency tells about where most of the data points lie, and variability tells how far apart the points are from each other.

Range and Interquartile Range

The range indicates statistical dispersion as the length of the smallest interval, which consists of all the data, and it is examined by subtracting the smallest observations from the greatest. We can measure the range in the same units we can measure data. There are three range types: the crude range, potential crude range, and observed crude range. The difference between the first and the third quartiles, also a measure of the statistical dispersion, is called the interquartile range. It is proved that the interquartile range is more stable than the range.

RangeInterquartile Range

The range indicates statistical dispersion as it is the length of the smallest interval which consists of all the data and it is examined by subtracting the smallest observations from the greatest

The difference between the first and the third quartiles and which is also a measure of the statistical dispersion is called the interquartile range.

Variance and Standard deviation

Variance is denoted by σ2. It assesses the spread or dispersion of scores within a population or sample. It is discovered that a big variance is suggestive of many more scores that are further from the mean and spread throughout a wider range. In contrast, a small variance is indicative of many relatively comparable scores that are all near the sample mean. S.D. stands for standard deviation. It is described as a measure of the variability of a group of values or scores, indicating how far they differ from the mean. A high standard deviation suggests that data points are dispersed throughout many different values, whereas a low standard deviation shows that data points cluster around the mean.

Role of Linear and Non-Linear Measures of Variability

The SW3, i.e., the Stepwatch3 Activity Monitor, is an instrument used to record the step counts from individuals walking in their living environment at a frequency. Originally the instrument SW3 was used to measure the volume of activity assembled during a recording period. To study this, researchers checked if SW3 data could be analyzed to brighten the control of walking activity. So, following that, they used a standard linear measure and two non-linear measures to check every minute of step count values collected from two inactive and two active adults over 14 days. The results showed that there is a difference between the linear and non-linear measures of the two groups. The standard deviation evaluated the variability as the diffusion of minute step counts is independent of a subsequent order.

Moreover, it was also found that the values of standard deviation for active subjects were much greater than the inactive subjects, indicating a wide range of control system output. The linear and non-linear measures indices described minute step count variability in terms of profane structure. Furthermore, when examined together, the linear and non-linear measures gave a greater presence of memory in the data of active subjects, indicating that the control of their walking activity produced more predictable and structured output patterns than that of the inactive subjects. Overall, the results suggested differences in the underlying control of their walking activity between active and inactive older adults. Linear and non-linear approaches for analyzing variability in step activity data present a new path for future motor control research.

Poorer Psychological Health is associated with Positive Emotion Variability

Researchers suggested that there is a relationship between positive emotion with flexible outcomes in several realms, which also include psychological health. However, its main focus is on overall levels of positive emotion, with less heed paid to how variable versus stable it is across time. Thus they examined the psychological health correlates of stability versus positive emotion variability across two different studies, populations, and scientifically approved approaches for examining variability in emotion across time. Study number 1 used a daily experience approach in a U.S. population sample (N = 240) to examine positive emotion variability across two weeks (macro level). Study number 2 used a daily reorganized method in a French adult sample (N = 2,391) to examine variability within two days (microlevel). Greater micro and macro level variability in positive emotion was associated with poor psychological health, including lower welfare and life satisfaction and greater anxiety and depression (From Study 1), and life satisfaction, lower daily satisfaction, and happiness (From Study 2). These findings support the concept that positive emotion variability plays a significant and cumulative role in psychological health above and beyond overall happiness levels and that too much variability might be dysfunctional.


The distance between data points within a distribution and their distance from its center is called "variability." In addition to measures of central tendency, measures of variability provide descriptive statistics that summarise your data. Other synonyms for a variance include spread, scatter, and dispersion. Thus, variability measurements are quite useful since they assist us in measuring the degree of departure already present in the data.