A random variable follows the normal probability distribution with a mean of 117 and a standard deviation of 23. Complete parts (a) through (d) below.
Click here to view page 1 of the standard normal probability table. Click here to view page 2 of the standard normal probability table.
a) What is the probability that a randomly selected value from this population is between 103 and 133?
(Round to four decimal places as needed.)
b) What is the probability that a randomly selected value from this population is between 124 and 161?
(Round to four decimal places as needed.)
c) What is the probability that a randomly selected value from this population is between 69 and 85?
(Round to four decimal places as needed.)
d) What is the probability that a randomly selected value from this population is between 109 and 165?
(Round to four decimal places as needed.)

Respuesta :

To solve these problems, we first need to standardize the values using the formula:

\[ Z = \frac{X - \mu}{\sigma} \]

where:
- \( X \) is the given value,
- \( \mu \) is the mean,
- \( \sigma \) is the standard deviation, and
- \( Z \) is the standardized value.

Then, we'll use the standard normal probability table to find the probabilities.

a) For \( X = 103 \) and \( X = 133 \):
\[ Z_1 = \frac{103 - 117}{23} = -0.609 \]
\[ Z_2 = \frac{133 - 117}{23} = 0.696 \]

Using the standard normal probability table, the probability between \( Z_1 \) and \( Z_2 \) is approximately 0.5279.

b) For \( X = 124 \) and \( X = 161 \):
\[ Z_1 = \frac{124 - 117}{23} = 0.304 \]
\[ Z_2 = \frac{161 - 117}{23} = 1.913 \]

The probability between \( Z_1 \) and \( Z_2 \) is approximately 0.4664.

c) For \( X = 69 \) and \( X = 85 \):
\[ Z_1 = \frac{69 - 117}{23} = -2.087 \]
\[ Z_2 = \frac{85 - 117}{23} = -1.391 \]

The probability between \( Z_1 \) and \( Z_2 \) is approximately 0.0822.

d) For \( X = 109 \) and \( X = 165 \):
\[ Z_1 = \frac{109 - 117}{23} = -0.348 \]
\[ Z_2 = \frac{165 - 117}{23} = 2.087 \]

The probability between \( Z_1 \) and \( Z_2 \) is approximately 0.8664.
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