A distribution of values is normal with a mean of 152.4 and a standard deviation of 47.9.

Find the probability that a randomly selected value is less than 272.2.
P(X < 272.2) =

Enter your answer as a number accurate to 4 decimal places. Answers obtained using exact z-scores or z-scores rounded to 3 decimal places are accepted.

1 answer

To find the probability that a randomly selected value \( X \) is less than 272.2 in a normal distribution with mean \( \mu = 152.4 \) and standard deviation \( \sigma = 47.9 \), we first need to calculate the z-score.

The z-score is calculated using the formula:

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

Substituting the given values:

\[ z = \frac{272.2 - 152.4}{47.9} = \frac{119.8}{47.9} \approx 2.497 \]

Next, we need to find the probability corresponding to this z-score. We can use a standard normal distribution table or a calculator to find \( P(Z < 2.497) \).

Using a z-table or calculator, we find:

\[ P(Z < 2.497) \approx 0.9933 \]

Thus, the probability that a randomly selected value is less than 272.2 is:

\[ P(X < 272.2) \approx 0.9933 \]

Finally, rounding to four decimal places, the answer is:

\[ \boxed{0.9933} \]