Question -
Answer -
Daily Pocket Allowance(in c) | 11-13 | 13-15 | 15-17 | 17-19 | 19-21 | 21-23 | 23-35 |
Number of children | 7 | 6 | 9 | 13 | f | 5 | 4 |
Solution:
To find out themissing frequency, use the mean formula.
Here, the value ofmid-point (xi)┬а mean┬аx╠Д┬а= 18
┬а
| Class interval | Number of children (fi) | Mid-point (xi) | ┬а┬а┬а fixi┬а┬а┬а┬а |
| 11-13 | 7 | 12 | 84 |
| 13-15 | 6 | 14 | 84 |
| 15-17 | 9 | 16 | 144 |
| 17-19 | 13 | 18 = A | 234 |
| 19-21 | f | 20 | 20f |
| 21-23 | 5 | 22 | 110 |
| 23-25 | 4 | 24 | 96 |
| Total | fi┬а= 44+f | | Sum fixi┬а= 752+20f |
The mean formula is
Mean = x╠Д = тИСfixi┬а/тИСfi┬а=(752+20f)/(44+f)
Now substitute thevalues and equate to find the missing frequency (f)
тЗТ 18 = (752+20f)/(44+f)
тЗТ 18(44+f) = (752+20f)
тЗТ 792+18f = 752+20f
тЗТ 792+18f = 752+20f
тЗТ 792 тАУ 752 = 20f тАУ 18f
тЗТ 40 = 2f
тЗТ f = 20
So, the missingfrequency, f = 20.