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Question -

Find the mean number of heads in three tosses of a fair coin.



Answer -

Given a coin is tossedthree times.

Three coins are tossedsimultaneously. Hence, the sample space of the experiment is S = {HHH, HHT,HTH, THH, TTH, THT, HTT, TTT}

X represents thenumber of heads.

As we see, X is afunction on sample space whose range is {0, 1, 2, 3}.

Thus, X is a randomvariable which can take the values 0, 1, 2 or 3.

P (X = 0) = P(TTT) = 1/8

P (X = 1) = P (TTH) +P (THT) + P (HTT) = 1/8 +1/8 + 1/8 = 3/8

P (X = 2) = P (THH) +P (HTH) + P (HHT) = 1/8 + 1/8 + 1/8 = 3/8

P (X = 3) = P (HHH) =1/8

Hence, the requiredprobability distribution is,

X

0

1

2

3

P (X)

1/8

3/8

3/8

1/8

Therefore mean μ is:

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