find the mean of the following data by shortcut method
marks | 20 | 22 | 25 | 30 | 35 | 39 | 45 | 50 | total | |
frequency | 4 | 6 | 8 | 10 | 8 | 7 | 5 | 2 | 50 |
Marks xi | Assumed mean (A) | Frequency f | fdi | |
20 | 20 – 35 = – 15 | 4 | (– 15) (4) = – 60 | |
22 | 22 – 35 = – 13 | 6 | (– 13) (6) = – 78 | |
25 | 25 – 35 = – 10 | 8 | (– 10) (8) = – 80 | |
30 | 30 – 35 = – 5 | 10 | (– 5) (10) = – 50 | |
35 | 35 | 35 – 35 = 0 | 8 | 0 (8) = 0 |
39 | 39 – 35 = 4 | 7 | 4 (7) = 28 | |
45 | 45 – 35 = 10 | 5 | 10 (5) = 50 | |
50 | 50 – 35 = 15 | 2 | 15 (2) = 30 |