Advertisements
Advertisements
प्रश्न
Given that the mean of the following frequency distribution is 30, find the missing frequency ‘f’.
| Class Interval | 0 - 10 | 10 - 20 | 20 - 30 | 30 - 40 | 40 - 50 | 50 - 60 |
| Frequency | 4 | 6 | 10 | f | 6 | 4 |
उत्तर
| Class interval |
Frequency (f) |
x | d = x - A | t = `"d"/"i"` | ft |
| 0 - 10 | 4 | 5 | - 30 | - 3 | - 12 |
| 10 - 20 | 6 | 15 | - 20 | - 2 | - 12 |
| 20 - 30 | 10 | 25 | - 10 | - 1 | - 10 |
| 30 - 40 | f | 35 = A | 0 | 0 | 0 |
| 40 - 50 | 6 | 45 | 10 | 1 | 6 |
| 50 - 60 | 4 | 55 | 20 | 2 | 8 |
Step deviation method,
∑f = 30 + f, A = 35, Class width (i) = 10
and ∑ft = - 34 + 14 = - 20
∴ Mean = A + `(sum "ft")/(sum "f") xx "i"`
`=> 30 = 35 + (- 20)/(30 + "f") xx 10`
`=> - 5 = (- 200)/(30 + "f")`
`=> 30 + "f" = 200/5`
⇒ 30 + f = 40
⇒ f = 40 - 30
⇒ f = 10
APPEARS IN
संबंधित प्रश्न
Thirty women were examined in a hospital by a doctor and the number of heartbeats per minute were recorded and summarized as follows. Fine the mean heartbeats per minute for these women, choosing a suitable method.
| Number of heartbeats per minute | 65 - 68 | 68 - 71 | 71 - 74 | 74 - 77 | 77 - 80 | 80 - 83 | 83 - 86 |
| Number of women | 2 | 4 | 3 | 8 | 7 | 4 | 2 |
The following table gives the literacy rate (in percentage) of 35 cities. Find the mean literacy rate.
| Literacy rate (in %) | 45 − 55 | 55 − 65 | 65 − 75 | 75 − 85 | 85 − 95 |
| Number of cities | 3 | 10 | 11 | 8 | 3 |
Find the mean of the following data, using direct method:
| Class | 0-100 | 100-200 | 200-300 | 300-400 | 400-500 |
| Frequency | 6 | 9 | 15 | 12 | 8 |
Find the mean of the following data, using assumed-mean method:
| Class | 0 – 20 | 20 – 40 | 40 – 60 | 60 – 80 | 80 – 100 | 100 - 120 |
| Frequency | 20 | 35 | 52 | 44 | 38 | 31 |
Find the correct answer from the alternatives given.
The formula to find mean from a grouped frequency table is \[X = A + \frac{\sum f_i u_i}{\sum f_i} \times hg\] .
What is the algebraic sum of deviation of a frequency distribution about its mean?
A school has 4 sections of Chemistry in class X having 40, 35, 45 and 42 students. The mean marks obtained in Chemistry test are 50, 60, 55 and 45 respectively for the 4 sections. Determine the overall average of marks per student.
Find the mean of the distribution:
| Class | 1 – 3 | 3 – 5 | 5 – 7 | 7 – 10 |
| Frequency | 9 | 22 | 27 | 17 |
The weights (in kg) of 50 wrestlers are recorded in the following table:
| Weight (in kg) | 100 – 110 | 110 – 120 | 120 – 130 | 130 – 140 | 140 – 150 |
| Number of wrestlers |
4 | 14 | 21 | 8 | 3 |
Find the mean weight of the wrestlers.
Find the mean of: 5, 2.4, 6.2, 8.9, 4.1 and 3.4
