Exploratory Data Analysis: Stem & Leaf Displays

In this video I explain stem-and-leaf displays or stemplots, which are part of exploratory data analysis developed by John W. Tukey. I explain the basic design of stem-and-leaf displays as well as several variations including back-to-back stem-and-leaf displays and stretched … Read More

How to Interpret (and Create) Frequency Distribution Tables

In this video I explain frequency distribution tables and grouped frequency distribution tables for summarizing data. I explain each of the columns, including the variable measured, the frequency, the proportion and percentage of the data at each variable, and the … Read More

n-1 Explained Conceptually

In this video I answer the common question of why we divide by n-1 when calculating variance from a sample, known as Bessel’s Correction. I focus on conceptual understanding of why this adjustment is needed and why n-1 is the … Read More

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