Mathematics
Mathematics
Problem
For a set of 80 observations grouped into the classes shown below, it is found that if each class mark is reduced by 50 and the result is multiplied by the corresponding frequency, the total of all such products is −320.| Class interval | 20–30 | 30–40 | 40–50 | 50–60 | 60–70 | 70–80 |
|---|---|---|---|---|---|---|
| Frequency | 12 | 18 | 20 | 15 | 10 | 5 |