Lesson 13 Descriptive Statistics Measures of Central Tendency and Dispersion Flashcards
Measures of Central Tendency
Measures of central tendency inform us about central values for a set of data. They are ‘averages’ – ways of calculating a typical value for set of data. The average can be calculated in different ways, each one appropriate for a different situation.
Mean
Adding all the scores and then dividing by the total number of scores
Advantage of the mean
Most accurate measurement and takes into account all scores
Disadvantage of the mean
Can be distorted by a single extreme value
Median
It is calculated by ranking all the scores in order and taking the middle value. If there is an even number of scores than the median is the mid-point between the two middle scores
Advantage of the median
Unaffected by extreme scores
Disadvantage of the median
The median is not as sensitive as the mean because not all scores are used in the calculation so it can be unrepresentative of the data if the scores are clustered around high and low levels.
Mode
Most frequent value in the data set
Advantage of the mode
Unaffected by extreme scores
Disadvantage of the mode
Tells us nothing about other scores in the data
Measures of Dispersion
A set of data can also be described in terms of how dispersed or spread out the data items are.
Range
Difference between the highest and lowest values in the data set
How to calculate the range in psychology
highest value - lowest value + 1
advantage of the range
quick and easy
disadvantage of the range
easily distorted by extreme values
