Statistics CBSE Questions & Answers

Statistics

This is Mathematics Class 09 Statistics CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
Vihaan has marks of 92, 85, and 78 in three mathematics tests. In order to have an average of exactly 87 for the four math tests, he should obtain
  • A
    91 marks
  • B
    90 marks
  • C
    92 marks
  • D
    93 marks
    Correct
2
If \(\bar x\) is the mean of \({x_1},{x_2},...,{x_n},\bar y\) is the mean of \({y_1},{y_2}...,{x_n},...,{y_{n'}}\) then \(\bar z\) th mean of \({x_1},{x_2}...,{x_n},{y_1},{y_2},...,{y_n}\) is equal to
  • A
    \({{\bar x + \bar y} \over {2n}}\)
  • B
    \({{\bar x + \bar y} \over n}\)
  • C
    \(\bar x + \bar y\)
  • D
    \({{\bar x + \bar y} \over 2}\)
    Correct
3
If \(\bar x\) is the mean of \({x_1},{x_2},...,{x_n}\) then for a \( \ne \)0, the mean of \(a{x_1},a{x_2},...,a{x_n},\) \({{{x_1}} \over a},{{{x_2}} \over a},...,{{{x_n}} \over a}\) is
  • A
    \(\left( {a + {1 \over a}} \right){{\bar x} \over n}\)
  • B
    \(\left( {a + {1 \over a}} \right)\bar x\)
  • C
    \(\left( {a + {1 \over a}} \right){{\bar x} \over 2}\)
    Correct
  • D
    \({{\left( {a + {1 \over a}} \right)\bar x} \over {2n}}\)
4
If the mean of x and \({1 \over x}\) is M, then the mean of \({x^2}\) and \({1 \over {{x^2}}}\) is
  • A
    \(2{M^2} - 1\)
    Correct
  • B
    \(2{M^2} + 1\)
  • C
    2M + 1
  • D
    2M – 1
5
If the mean of x and \({1 \over x}\) is M, then the mean of \({x^3}\) and \({1 \over {{x^3}}}\) is
  • A
    \(3{M^3} - 4M\)
  • B
    \(4{M^3} + 3M\)
  • C
    \(4{M^3} - 3M\)
    Correct
  • D
    \(3{M^3} + 4M\)
6
The mean of six numbers is 23. If one of the numbers is excluded, the mean of the remaining numbers becomes 20. The excluded number is
  • A
    38
    Correct
  • B
    37
  • C
    39
  • D
    36
7
The mean of five observations is 15. If the mean of first three observations is 14 and that of last three is 17, then the third observation is
  • A
    31
  • B
    18
    Correct
  • C
    32
  • D
    29
8
The mean of 50 observations is 39. If one of the observations which was 23 was replaced by 43, the resulting mean will be
  • A
    38.4
  • B
    40.3
  • C
    39.4
    Correct
  • D
    39
9
There are 50 numbers. Each number is subtracted from 53 and the mean of the numbers so obtained is found to be – 3.5. The mean of the given number is
  • A
    56.5
    Correct
  • B
    52.5
  • C
    49.5
  • D
    47.5
10
The mean of n observations is\(\bar x\). If the first item is increased by 1, second by 2, third by 3 and so on, then the new mean is
  • A
    \(\bar x + {{n + 1} \over 2}\)
    Correct
  • B
    \(\bar x + {n \over 2}\)
  • C
    \(\bar x + {{n(n + 1)} \over 2}\)
  • D
    \(\bar x + n\)
11
The mean of the above frequency distribution is 3.5, then the value of x is
Question 11 figure 1
  • A
    2
  • B
    3
    Correct
  • C
    4
  • D
    5
12
If the mean of the observations: x, x + 3, x + 5, x + 7, x + 10 is 9, the mean of last three observations is
  • A
    \(10{2 \over 3}\)
  • B
    \(10{1 \over 3}\)
  • C
    \(11{2 \over 3}\)
  • D
    \(11{1 \over 3}\)
    Correct
13
The traffic police recorded the speed (in km/h) of 10 motorists as 48, 52, 57, 55, 42, 39, 60, 49, 53 and 47. Later an error in recording instrument was found. If the instrument has recorded the speed 5 km/h less in each case, then the correct average speed of the motorists is
  • A
    54.5 km/h
  • B
    52.5 km/h
  • C
    50.2 km/h
  • D
    55.2 km/h
    Correct
14
The difference between the mean and median of first five prime numbers is
  • A
    0.8
  • B
    1
  • C
    0.6
    Correct
  • D
    0.4
15
When the data consists of 3, 4, 5, 4, 3, 4, 5, which statement is true ?
  • A
    mean > mode
  • B
    Mean = mode
    Correct
  • C
    Median < mode
  • D
    Mean > median