Advertisements
Advertisements
प्रश्न
Answer the following :
Given below is the frequency distribution of marks obtained by 100 students. Compute arithmetic mean and S.D.
| Marks | 40 - 49 | 50 - 59 | 60 - 69 | 70 - 79 | 80 - 89 | 90 - 99 |
| No. of students | 4 | 12 | 25 | 28 | 26 | 5 |
Advertisements
उत्तर
Since data is not continuous, we have to make it continuous.
Let u = `(x - "A")/"h" = (x - 74.5)/10`
Calculation of variance of u:
| Marks C. I. |
Mid value (xi) |
No. of students (fi) |
ui = `(x_"i" - 74.5)/10` | fiui | fiui2 |
| 39.5 - 49.5 | 44.5 | 4 | −3 | −12 | 36 |
| 49.5 - 59.5 | 54.5 | 12 | −2 | −24 | 48 |
| 59.5 - 69.5 | 64.5 | 25 | −1 | −25 | 25 |
| 69.5 - 79.5 | 74.5 | 28 | 0 | 0 | 0 |
| 79.5 - 89.5 | 84.5 | 26 | 1 | 26 | 26 |
| 89.5 - 99.5 | 94.5 | 5 | 2 | 10 | 20 |
| N = 100 | `sumf_"i"u_"i"` = – 25 | `sumf_"i"u_"i"^2` = 155 |
`bar(u) = (sumf_"i"u_"i")/"N" = (-25)/100` = – 0.25
`bar(x) = bar(u) xx "h" + "A"`
= – 0.25 × 10 + 74.5
= 72
Var (u) = `sigma_u^2 = (sumf_"i"u_"i"^2)/"N" - (baru)^2`
= `155/100 - (-0.25)^2`
= 1.55 – 0.0625
= 1.4875
∴ Var (X) = h2 var (u) = (10)2 × 1.4875
= 100 × 1.4875
= 148.75
∴ S.D. = `sigma_x = sqrt("Var(X)")`
= `sqrt(148.75)`
= 12.2
APPEARS IN
संबंधित प्रश्न
Find variance and S.D. for the following set of numbers:
7, 11, 2, 4, 9, 6, 3, 7, 11, 2, 5, 8, 3, 6, 8, 8, 2, 6
Find variance and S.D. for the following set of numbers:
65, 77, 81, 98, 100, 80, 129
Compute variance and standard deviation for the following data:
| X | 2 | 4 | 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 |
| F | 8 | 10 | 10 | 7 | 6 | 4 | 3 | 4 | 2 | 6 |
Compute the variance and S.D.
| X | 31 | 32 | 33 | 34 | 35 | 36 | 37 |
| Frequency | 15 | 12 | 10 | 8 | 9 | 10 | 6 |
Find the variance and S.D. of the following frequency distribution which gives the distribution of 200 plants according to their height:
| Height (in cm) | 14 – 18 | 19 – 23 | 24 – 28 | 29 – 33 | 34 – 38 | 39 – 43 | 44 – 48 |
| No. of plants | 5 | 18 | 44 | 70 | 36 | 22 | 5 |
The mean of 5 observations is 4.8 and the variance is 6.56. If three of the five observations are 1, 3 and 8, find the other two observations
Select the correct option from the given alternatives :
The standard deviation of a distribution divided by the mean of the distribution and expressing in percentage is called:
Select the correct option from the given alternatives :
If the S.D. of first n natural numbers is `sqrt(2)`, then the value of n must be ––––––.
Select the correct option from the given alternatives :
For any two numbers, SD is always
Answer the following :
Find variance and S.D. for the following set of numbers:
25, 21, 23, 29, 27, 22, 28, 23, 21, 25
Answer the following :
Find variance and S.D. for the following set of numbers: 125, 130, 150, 165, 190, 195, 210, 230, 245, 260
Answer the following :
Following data gives no. of goals scored by a team in 100 matches. Compute the standard deviation
| No. of Goals Scored | 0 | 1 | 2 | 3 | 4 | 5 |
| No. of matches | 5 | 20 | 25 | 15 | 20 | 5 |
Answer the following :
Compute the variance and S.D. for the following data:
| X | 62 | 30 | 64 | 47 | 63 | 46 | 35 | 28 | 60 |
| F | 5 | 8 | 3 | 4 | 5 | 7 | 8 | 3 | 7 |
Find the Standard Deviation of the following data: 14, 22, 9, 15, 20, 17, 12, 11.
If a r.v. X has p.d.f., f(x) = `1/(xlog3)`, for 1 < x < 3, then E(X) and Var(X) are respectively ______
The S.D. and C.V. for the following frequency distribution is
| xi | 60 | 61 | 62 | 63 | 64 | 65 | 66 |
| fi | 3 | 10 | 11 | 13 | 7 | 5 | 1 |
The S.D. of 20 items is 15 and if each item is decreased or increased by 1, then standard deviation will be ______.
The standard deviation of the data 8, 7, 1, 15, 14, 10, 12 is ______.
For certain data, the following information is available. Obtain the combined standard deviation.
| X | Y | |
| Mean | 13 | 17 |
| S.D. | 3 | 2 |
| Size | 20 | 30 |
If the S.D. of the data 1, 2, 4, 5, 6, 7, 9 is 2.59, then the S.D. of 3, 6, 12, 15, 18, 21, 27 is ______.
If the mean of the data 7, 7, 9, 7, 8, 7, λ, 8 is 7, then the variance of this data is ______.
The mean and standard deviation of 50 observations are 15 and 2 respectively. It was found that one incorrect observation was taken such that the sum of correct and incorrect observations is 70. If the correct mean is 16, then the correct variance is equal to ______.
The mean of a set of observation is `overlinex`. If each observation is divided by α, α ≠ 0 and then is increased by 10, then the mean of the new set is ______.
Let x1, x2 ,..., xn be n observations such that `sumx_1^2` = 400 and `sumx_i` = 80. Then, a possible value of n among the following is:
The variance of first n natural numbers is ______.
