# Normal distribution 2

(a) A coin is tossed 81 times. What is the probability that the number of heads will differ from 40.5 by 5.5 or less ?

(b) A coin is tossed 810 times. What is the probability that the number of heads will differ from 405 by 55 or less ?

### 1 Answer

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- 六呎將軍Lv 71 decade agoFavorite Answer
(a) μ = 40.5

σ = √[81 x 0.5 x (1 - 0.5)]

= 4.5

Now, 5.5 is 1.222 times of the standard deviation, in accordance to the normal distribution table, the required probability is 0.7784.

(b) μ = 405

σ = √[810 x 0.5 x (1 - 0.5)]

= 14.23

Now, 55 is 3.865 times of the standard deviation, in accordance to the normal distribution table, the required probability is almost equal to 1.

Source(s): Myself

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