Statistics

1

A box contains 15 green and 10 yellow balls. If 10 balls are randomly drawn, one-by-one, with replacement, then the variance of the number of green balls drawn is:

  1. 12/5
  2. 6
  3. 4
  4. 6/25
2

The mean and variance of a random variable X having binomial distribution are 4 and 2 respectively, then P (X = 1) is

  1. 1/4
  2. 1/8
  3. 1/16
  4. 1/32
3

If the mean deviation about the median of the numbers a, 2a,..., 50a is 50, then |a| equals

  1. 2
  2. 3
  3. 4
  4. 5
4

The average marks of boys in class is 52 and that of girls is 42. The average marks of boys and girls combined is 50. The percentage of boys in the class is

  1. 20
  2. 40
  3. 60
  4. 80
5

If the mean deviation of the numbers 1, 1 + d, 1 + 2d,... , 1 + 100d from their mean is 255, then the d is equal to

  1. 10
  2. 10.1
  3. 20
  4. 20.2
6

In a frequency distribution, the mean and median are 21 and 22 respectively, then its mode is approximately

  1. 25.5
  2. 24.0
  3. 22.0
  4. 20.5
7

In a class of 100 students there are 70 boys whose average marks in a subject are 75. If the average marks of the complete class is 72, then what is the average of the girls?

  1. 74
  2. 65
  3. 68
  4. 73
8

The median of a set of 9 distinct observations is 20.5. If each of the largest 4 observations of the set is increased by 2, then median of the new set

  1. is two times the original median
  2. is increased by 2
  3. remains the same as that of the original set
  4. is decreased by 2
9

If the standard deviation of the numbers 2, 3, a and 11 is 3.5, then which of the following is true?

  1. 3a2 – 32a + 84 = 0
  2. 3a2 – 34a + 91 = 0
  3. 3a2 – 23a + 44 = 0
  4. 3a2 – 26a + 55 = 0