Subject: Statistics
Created by: Marija Stanojcic
Revised: 10/9/2018
Mean, median, mode, variance & standard deviation
MEAN – average value of the data set
symbol(s):
– sample mean,
Example 1: Calculate the mean for the data set: 1, 4, 4, 6, 10.
=
=
MEDIAN – “the middle number”, a number that splits data set in half
How to find median?
Step 1: Arrange data in increasing order
Step 2: Determine how many numbers are in the data set = n
Step 3: If n is odd: Median is the middle number
If n is even: Median is the average of two middle numbers
Example 2: Find the median for the data set: 34, 22, 15, 25, 10.
Step 1: Arrange data in increasing order 10, 15, 22, 25, 34
Step 2: There are 5 numbers in the data set, n = 5.
Step 3: n = 5, so n is an odd number Median = middle number, median is 22.
Example 3: Find the median for the data set: 19, 34, 22, 15, 25, 10.
Step 1: Arrange data in increasing order 10, 15, 19, 22, 25, 34
Step 2: There are 6 numbers in the data set, n = 6.
Step 3: n = 6, so n is an even number Median = average of two middle numbers
median =
= 20.5
Notes: Mean and median don’t have to be numbers from the data set!
Mean and median can only take one value each.
Mean is influenced by extreme values, while median is resistant.