Types of variation
The table below summarises monthly rainfall data in a city over several years:
Month | Mean | Standard deviation |
---|---|---|
January | 32.13 | 2.11 |
February | 31.44 | 2.17 |
March | 31.24 | 2.08 |
April | 30.46 | 1.73 |
May | 28.53 | 1.69 |
June | 26.10 | 1.37 |
July | 26.43 | 1.32 |
August | 30.04 | 1.28 |
September | 33.44 | 1.24 |
October | 34.93 | 1.01 |
November | 34.34 | 1.49 |
December | 32.62 | 1.75 |
Overall | 30.99 | 3.17 |
We can distinguish between three types of variation in the rainfalls: