\( X \) is a normally distributed random variable with mean 22 and standard deviation 9 . What is the probability that \( X \) is between 30 and \( 67 ? \) Write your answer as a decimal rounded to the nearest thousandth.
Solución de tutoría real
Responder
Solución
Revisado y aprobado por el equipo de tutoría de UpStudy
Bonus Knowledge
To find the probability that \( X \) is between 30 and 67 in a normal distribution, we first standardize these values using the z-score formula: \[ z = \frac{(X - \mu)}{\sigma} \] For \( X = 30 \): \[ z_{30} = \frac{(30 - 22)}{9} = \frac{8}{9} \approx 0.889 \] For \( X = 67 \): \[ z_{67} = \frac{(67 - 22)}{9} = \frac{45}{9} = 5 \] Next, we use the standard normal distribution table to find the probabilities corresponding to these z-scores. - The probability corresponding to \( z_{30} \approx 0.889 \) is approximately 0.813. - The probability corresponding to \( z_{67} = 5 \) is very close to 1 (as values this high are extremely rare in a normal distribution). Therefore, the probability that \( X \) is between 30 and 67 is: \[ P(30 < X < 67) = P(Z < 5) - P(Z < 0.889) \approx 1 - 0.813 = 0.187 \] Rounded to the nearest thousandth, the final answer is: \[ \boxed{0.187} \]