NCERT Class XI Mathematics - Probability - Solutions

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Question : 24
Total: 54
Which of the following cannot be valid assignment of probabilities for outcomes of sample space S = {ω1,ω2,ω3,ω4,ω5,ω6,ω7}
Assignment ω1 ω2 ω3 ω4 ω5 ω6 ω7
(a) 0.10.01 0.05 0.03 0.010.2 0.6
(b) 1/71/71/7 1/71/7 1/7 1/7
(c) 0.10.2 0.30.40.50.60.7
(d) - 0.1 0.20.3 0.4- 0.2 0.1 0.3
(e) 1/14 2/14 3/14 4/14 5/14 6/1415/14

Solution:  
(a) Sum of probabilities
= 0.1 + 0.01 + 0.05 + 0.03 + 0.01 + 0.2 + 0.6 = 1.00
∴ Assignment of probabilities is valid.
(b) Sum of probabilities
=
1
7
+
1
7
+
1
7
+
1
7
+
1
7
+
1
7
+
1
7
=
7
7
= 1
∴ Assignment of probabilities is valid.
(c) Sum of probabilities
= 0.1 + 0.2 + 0.3 + 0.4 + 0.5 + 0.6 + 0.7 = 2.8
Sum of probabilities is greater than 1.
∴ This assignment of probabilities is not valid.
(d) Probability of any event cannot be negative. Therefore, this assignment of probabilities is not valid.
(e) The last probability
15
14
is greater than 1.
∴ This assignment of probabilities is not valid.
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