- Find the mean (In this example it is 1+2+3+4+5/5 = 3)
- Find the total amount of data (In this example there are 5 as there are 5 given modes of transport, therefore N = 5)
- To complete the top half of the fraction, , add an extra column to the table. For each piece of data subtract the given value from the mean ( in this example) and square the result
i.e. car = 2 people, so (2 – mean(3)) 2 = 4
- Add up the total of all the results from step 3 (The sum of) This result can now replace the top half of the fraction ( in this example, it’s 4+1+0+1+4=10)
- To find the bottom half of the fraction, like the equation says to do so subtract 1 from the total amount of data in the dataset, 5-1 = 4
- The fraction should look like this now:
- Pop all the calculation into the calculator
e.g.
How do you get to school? | Total | |
Bus | 1 | (1-3)2 = 4 |
Car | 2 | (2-3)2 = 1 |
Bike | 3 | (3-3)2 = 0 |
Walk | 4 | (4-3)2 = 1 |
Helicopter | 5 | (5-3)2 = 4 |
Total | 15 | 10 |
n = 5-1 = 4
S = 1.58