The random variable X is normally distributed with a mean of 70 and a standard deviation of 10. What is the probability that X is between 72 and 84? (a) 0.683 (b) 0.954 (c) 0.271 (d) 0.340

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The probability that the X is between 72 and 84 is 0.340 , the correct option is (d) .

In the question ,

it is given that ,

The random variable X is said to be normally distributed  ,

the mean is given as , μ = 70 , and

standard deviation of normal distribution is  (σ) = 10

probability that X is between 72 and 84 is written as P(72 < X < 84)

= P((72 - 70)/10 [tex]<[/tex] Z [tex]<[/tex] (84 - 70)/10)

= P(0.2 < Z < 1.4)

= P(0 [tex]<[/tex] Z [tex]<[/tex] 1.4) – P(0 [tex]<[/tex] Z [tex]<[/tex] 0.2)

From the z table , we get the values as

= 0.4192 – 0.0793

= 0.3399

≈ 0.340

Therefore , The probability that the X is between 72 and 84 is 0.340 , the correct option is (d) .

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