Unit-7:Probability and Statistics
Q1.
Three unbiased coins are tossed together. Find the probability of getting at least two heads.
(a) 3/4 (b) 3/8 (c) 1/4
(d) 1/2
Solution.
S = {HHH, HHT, HTH, THH, TTH, THT, HTT, TTT}
A = at least 2 heads
A = {HHH, HHT, HTH, THH}
n(S) = 8
n(A) = 4
P(A) = n(A)/n(S)
= 4/8
= 1/2
Solution
Q2.
A bag contains cards which are numbered from 6 to 80. A card is drawn at random from the bag. Find the probability that it has 2 digit number.
(a) 6/80 (b) 71/76 (c) 71/75 (d) 63/100
Solution.
n(S) = 75
n(A) = 71
P(A) = n(A)/n(S)
= 71/75
Solution
Q3.
An unbaised coin tossed 10 times find the probability getting 11 heads.
(a) 0 (b) 1 (c) 1/2 (d) 10/11
Solution.
(a) 0
Solution
Q4.
P(A) + P(not A) = _________ .
(a) 1 (b) 0 (c) 1/2 (d) 2/3
Solution.
(a) 1
Solution
Q5.
In the given figure, a ball is thrown and lands in the interior of the circle what is the probability that the ball will land in the unshaded region
(a) 19/14π (b) 0 (c) 1 (d) 48/25π
Solution.
2r = AC = 5
r = 5/2
Area of the circle = π25/4 = 25π/4 cm
2 Area of the rectangle = 12 cm
2
P(Ball land in the unshaded part) =
Area of unshaded part /Whole area (Area of the circle)
12 /25π/4
48 /25π
Solution
Q6.
The arithmetic mean of 1,2,3,-------n is .
(a) (2n + 1)/2 (b) (n+1)/2 (c) n/2 (d) n
Solution.
= Sum of first n natural number
= n(n + 1)/2
A.M = {n(n + 1)/2}/n
= (n + 1)/2
Solution
Q7.
Which of the following is not a measure of central tendency.
(a) Mean (b) S.D (c) Median (d) Mode
Solution.
(b) S.D
Solution
Q8.
Intersection of less than ogive curve and more than ogive curve gives
(a) Median (b) Mode (c) S.D (d) Mean
Solution.
(a) Median
Solution
Q9.
The mode of a frequency distribution can be determined graphically from.
(a) ogive (b) frequency curve (c) frequency polygon
(d) histogram
Solution.
(d) histogram
Solution
Q10.
The mean of first n odd natural number is
(a) n + 1 (b) n2 (c) n (d) 2n
Solution.
Mean = n2/n
= n
Solution
