Inclusive vs. Exclusive Interquartile Range

In this video I explain the difference between calculating an exclusive interquartile range and an inclusive interquartile range. While we generally use an exclusive interquartile range with an even set of scores, when we have an odd-numbered set of scores … Read More

Dispersion for Nominal Data: The Variation Ratio

In this video I describe how we can describe dispersion or variability in nominal data by calculating a variation ratio. This is a simple measure of spread that tells us the frequency of scores that differ from the mode, which … Read More

Understanding Central Tendency

In this video I explain the strengths and limitations of the 3 measures of central tendency: the mean, the median, and the mode. This is part of a key theme of statistics, which is the importance of the choices researchers … Read More

The Ordinal vs. Interval Debate in Psychology

In this video I describe how psychologists and social scientists often treat ordinal data as if it were interval data, which is a cause of some debate between pure statisticians and more pragmatic researchers. I discuss why this may or … Read More

Is Peripheral Vision in Color or Black and White?

In this video I discuss peripheral color vision, including the common misconception that peripheral vision is completely black and white. By looking at the distribution of rods and cones throughout the retina, we can see that color vision extends to … Read More

Scales of Measurement or Types of Data

In this video I describe the 4 scales of measurement proposed by Stanley Smith Stevens, which have become the standard way of defining types of data. These include nominal, ordinal, interval, and ratio. I discuss the defining features of each, … Read More