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NCERT Solutions for class 11 Maths | Chapter 15 - Statistics

(1) What should be the modal class

[A] 10-20
[B] 30-40
[C] 40-50
[D] 50-60
Answer: 30-40
(2) The abscissa of the point of interaction of the ‘less than type’ and of the ‘more than type’ cumulative frequency curve of grouped data gives
[A] mode
[B] median
[C] mean
[D] all of the above
Answer: median

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(3) Construction of a cumulative frequency table is useful determining the
[A] mean
[B] mode
[C] medien
[D] all of the above
Answer: medien
(4) The mean deviation of the data 3, 10, 10, 4, 7, 10, 5 from the mean is
[A] 2
[B] 2.57
[C] 3
[D] 3.57
Answer: 2.57
(5) The mean of 100 observations is 50 and their standard deviation is 5. The sum of all squares of all the observations is
[A] 50,000
[B] 250,000
[C] 252500
[D] 255000
Answer: 252500
(6) Consider the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. If 1 is added to each number, the variance of the numbers so obtained is
[A] 6.5
[B] 2.87
[C] 3.87
[D] 8.25
Answer: 8.25
(7) Consider the first 10 positive integers. If we multiply each number by −1 and then add 1 to each number, the variance of the numbers so obtained is
[A] 8.25
[B] 6.5
[C] 3.87
[D] 2.87
Answer: 8.25
(8) The standard deviation of first 10 natural numbers is
[A] 5.5
[B] 3.87
[C] 2.97
[D] 2.87
Answer: 2.87
(9) If the S.D. of a set of observations is 8 and if each observation is divided by −2, the S.D. of the new set of observations will be
[A] −4
[B] −8
[C] 8
[D] 4
Answer: 4
(10) Let x1, x2 , ...,xn be values taken by a variable X and y1, y2, ..., yn be the values taken by a variable Y such that yi= axi+ b, i = 1, 2,..., n. Then,
[A] Var (Y) = a2 Var (X)
[B] Var (X) = a2 Var (Y)
[C] Var (X) = Var (X) + b
[D] none of these
Answer: Var (Y) = a2 Var (X)
(11) The sum of the squares deviations for 10 observations taken from their mean 50 is 250. The coefficient of variation is
[A] 10 %
[B] 40 %
[C] 50 %
[D] none of these
Answer: 10 %
(12) The mean deviation of the numbers 3, 4, 5, 6, 7 from the mean is
[A] 25
[B] 5
[C] 1.2
[D] 0
Answer: 1.2
(13) A batsman scores runs in 10 innings as 38, 70, 48, 34, 42, 55, 63, 46, 54 and 44. The mean deviation about mean is
[A] 8.6
[B] 6.4
[C] 10.6
[D] None of these
Answer: None of these
(14) The mean deviation from the median is
[A] equal to that measured from another value
[B] maximum if all observations are positive
[C] greater than that measured from any other value.
[D] less than that measured from any other value.
Answer: less than that measured from any other value.
(15) The mean deviation of the data 2, 9, 9, 3, 6, 9, 4 from the mean is
[A] 2.23
[B] 2.57
[C] 3.23
[D] 3.57
Answer: 2.57
(16) Mean deviation for n observations x1 , x2 , ..........., xn from their mean x is given by
[A] ∑(xi - x) where (1 ≤ i ≤ n)
[B] {∑|xi - x|}/n where (1 ≤ i ≤ n)
[C] ∑(xi - x)2 where (1 ≤ i ≤ n)
[D] {∑(xi - x)2 }/n where (1 ≤ i ≤ n)
Answer: {∑|xi - x|}/n where (1 ≤ i ≤ n)
(17) One of the methods of determining mode is
[A] Mode = 2 Median - 3 Mean
[B] Mode = 2 Median + 3 Mean
[C] Mode = 3 Median - 2 Mean
[D] Mode = 3 Median + 2 Mean
Answer: Mode = 3 Median - 2 Mean
(18) If the mean of the following data is 20.6, then the value of p is

x: 10 15 p 25 35

f: 3 10 25 7 5

[A] 30
[B] 20
[C] 25
[D] 10
Answer: 20
(19) In a symmetric distribution
[A] Mean ≠ Median = Mode
[B] Mean = Median ≠ Mode
[C] Mean ≠ Median ≠ Mode
[D] Mean = Median = Mode
Answer: Mean = Median = Mode
(20) The algebraic sum of the deviation of 20 observations measured from 30 is 2. So, the mean of observations is
[A] 30.0
[B] 30.1
[C] 30.2
[D] 30.3
Answer: 30.1

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