The number of telephone calls received at an exchange per interval for 250 successive one-minute intervals are given in the following frequency table
Find mean
| No. of calls (x) | 0 | 1 | 2 | 3 | 4 | 5 | 6 |
| No. of intervals (f) | 15 | 24 | 29 | 46 | 54 | 43 | 39 |
1
3.74
2
3.84
3
3.54
4
4.00