Let X denote the number of scores which exceed 4 in 1 toss of a symmetrical die. Consider the following statements : 1. The arithmetic mean of X is 6. 2. The standard deviation of X is 2. Which of the above statements is/are correct ?
A
1 only
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B
2 only
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C
Both 1 and 2
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D
Neither 1 nor 2
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Solution
The correct option is C Neither 1 nor 2 The only possible favorable outcomes are 5 and 6. Hence, the arithmetic mean of X is 5.5.
The standard deviation of X=12((6−5.5)2+(5−55)2)=0.25