Advertisements
Advertisements
Question
Find the mean of the following frequency distribution:
| Class: | 10 – 15 | 15 – 20 | 20 – 25 | 25 – 30 | 30 – 35 |
| Frequency: | 4 | 10 | 5 | 6 | 5 |
Solution
| Class | Mid-point `(bbx_i)` |
`bb(f_i)` | `bb(d_i = x_i - A)` | `bb(f_i d_i)` |
| 10 – 15 | 12.5 | 4 | – 10 | – 40 |
| 15 – 20 | 17.5 | 10 | – 5 | – 50 |
| 20 – 25 | 22.5 = A | 5 | 0 | 0 |
| 25 – 30 | 27.5 | 6 | 5 | 30 |
| 30 – 35 | 32.5 | 5 | 10 | 50 |
| Total | `sumf_i` = 30 | `sumf_i d_i` = – 10 |
Here, assumed mean, A = 22.5
Mean = `A + (sumf_i d_i)/(sumf_i)`
= `22.5 + (-10)/30`
= 22.5 – 0.33
= 22.17
APPEARS IN
RELATED QUESTIONS
Frequency distribution of daily commission received by 100 salesmen is given below :
|
Daily Commission (in Rs.) |
No. of Salesmen |
| 100-120 | 20 |
| 120-140 | 45 |
| 140-160 | 22 |
| 160-180 | 09 |
| 180-200 | 04 |
Find mean daily commission received by salesmen, by the assumed mean method.
Find the mean from the following frequency distribution of marks at a test in statistics:
| Marks(x) | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 |
| No. of students (f) | 15 | 50 | 80 | 76 | 72 | 45 | 39 | 9 | 8 | 6 |
During a medical check-up, the number of heartbeats per minute of 30 patients were recorded and summarized as follows:
| Number of heartbeats per minute |
65 – 68 | 68 – 71 | 71 – 74 | 74 – 77 | 77 – 80 | 80 – 83 | 83 - 86 |
| Number of patients |
2 | 4 | 3 | 8 | 7 | 4 | 2 |
Find the mean heartbeats per minute for these patients, choosing a suitable method.
Find the mean of the following frequency distribution using step-deviation method
| Class | 0 – 10 | 10 – 20 | 20 – 30 | 30 – 40 | 40 – 50 |
| Frequency | 7 | 10 | 15 | 8 | 10 |
The mean of n observation is `overlineX`. If the first observation is increased by 1, the second by 2, the third by 3, and so on, then the new mean is
If the mean of observation \[x_1 , x_2 , . . . . , x_n is x\] then the mean of x1 + a, x2 + a, ....., xn + a is
There are 45 students in a class, in which 15 are girls. The average weight of 15 girls is 45 kg and 30 boys is 52 kg. Find the mean weight in kg of the entire class.
di is the deviation of xi from assumed mean a. If mean = `x+(sumf_id_i)/(sumf_i),` then x is ______.
Find the mean of the following data using assumed mean method:
| Class | 0 – 5 | 5 – 10 | 10 – 15 | 15 – 20 | 20 – 25 |
| Frequency | 8 | 7 | 10 | 13 | 12 |
Find the mean of the following frequency distribution:
| Class | 1 – 5 | 5 – 9 | 9 – 13 | 13 – 17 |
| Frequency | 4 | 8 | 7 | 6 |
