The standard deviation is the commonly used measure of variability when working with numeric data. It indicates how much, on average, each score in a set varies from the mean value of that set. It is usually represented by “s” or SD and is indicated as a +/- value. This single value demonstrates how much variability or dispersion is among scores in a set. To calculate the value, we must compute the deviation of each score from the mean and…
A common struggle for novice statisticians is choosing a measure of central tendency that is most appropriate in a given situation. It depends on the type of data you have and some basic data distribution characteristics. If your data values are categories or descriptive words (e.g., political party, eye color, the country where you were born), the mode is your best option. Categorical data is information that fits into finite options in which only one option can be true at…
The mode is the central tendency measure that indicates the data point that occurs most frequently in a set of scores. It measures the frequency of occurrence of each unique value and denotes the score that has the highest frequency. The data points that the mode can describe can be numeric (e.g., height in cm or weight in pounds) or word-based (e.g., eye color, the city in which you live). The data points are organized somehow, and the frequency of…
The median is another measure of central tendency representing the “middle score” in a set. It’s the point in a score distribution in which 50% of the scores fall below it and 50% fall above it. The median is usually represented by Md. but can sometimes be represented by M. Computing the median is a two-step process: List all the scores in order, starting with the highest value and progressing to the lowest. For example: 100, 88, 76, 65, 40, 25,…
The mean is the most commonly used measure of central tendency and is considered a descriptive statistic. In practical terms, it is the sum of all the values in a data set divided by the number of values. It is a single value that can summarize the value of many of the scores in the data set. It represents the middle of the score distribution, hence the term “measure of central tendency.” A simple version of the formula would be:…