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Measures of Central Tendency and Dispersion. Unit 8 – Statistics. Mean. The “average” of a bunch of numbers. To calculate: Add up all values Divide the sum by the total number of values in the data set. Write the answer using, “x-bar,” x. Median. The middle data point in a set of data.
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Measures of Central Tendency and Dispersion Unit 8 – Statistics
Mean • The “average” of a bunch of numbers. • To calculate: • Add up all values • Divide the sum by the total number of values in the data set. • Write the answer using, “x-bar,” x
Median • The middle data point in a set of data. • This can only be found once the data is in numerical order!
Median: • When there is an even number of data points, you must mind the mean of the middle two values
Mode • The number that occurs the most often number of times. • If there is a tie, then both numbers are the mode. • If every number only appears once, then there is no mode.
STOP: RE-GROUP • What is mean, median, and mode? • How do you find each of them?
What is the mean, median, and mode of the data below? 12, 14, 22, 25, 19, 32, 10, 21, 13, 22 Mean: Median: Mode:
Range • The difference between the largest number (maximum) in the data and the smallest number (minimum) in the data. • Describes the spread of the data. Range = Maximum - Minimum
Mean Absolute Deviation • Find the mean of the data. • Take each data point and subtract the mean. • Take the absolute value. (all answers should be positive now) • Add all of the absolute differences together. • Divide by the number of data points. • Describes how far, on average, the data points are away from the mean
Example #1 • The table shows running times for science-fiction movies. Find the mean absolute deviation for the data.
STOP: RE-GROUP • What is mean absolute deviation? • How do you find it?
Example #2 • Find the Mean Absolute Deviation of the quiz scores given below. 90, 97, 81, 78, 85 On average, quiz scores are about 6 points away from the mean.