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Suppose a normal distribution has a mean of 79 and a standard deviation of

7. What is P(X$ 65)?
• A. 0.84
• B. 0.025
• C. 0.975
• D. 0.16

1 Answer

2 votes

Answer: To find the probability that a normally distributed random variable X with mean 79 and standard deviation 7 is less than 65, we need to standardize the value 65 using the z-score formula:

z = (x - mu) / sigma

where x is the value we want to standardize, mu is the mean, and sigma is the standard deviation.

Plugging in the values we get:

z = (65 - 79) / 7

z = -14 / 7

z = -2

Using a standard normal distribution table, we can find that the probability of a standard normal random variable being less than -2 is approximately 0.0228.

Therefore, P(X < 65) = P(Z < -2) ≈ 0.0228.

The answer is not one of the given options, but it is closest to option B (0.025), which represents the probability of a standard normal random variable being less than -1.96.

Explanation:

User Janis Elsts
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