\( X \) is a normally distributed random variable with mean 26 and standard deviation 9 . What is the probability that \( X \) is greater than \( 6 ? \) Write your answer as a decimal rounded to the nearest thousandth.
Real Tutor Solution
Answer
Solution
Reviewed and approved by the UpStudy tutoring team
Beyond the Answer
To find the probability that \( X \) is greater than \( 6 \), we first need to standardize \( X \) using the z-score formula: \[ z = \frac{X - \mu}{\sigma} \] In this case, \( \mu = 26 \) (mean) and \( \sigma = 9 \) (standard deviation). For \( X = 6 \): \[ z = \frac{6 - 26}{9} = \frac{-20}{9} \approx -2.222 \] Next, we can use the standard normal distribution table or a calculator to find the probability that \( Z \) (the standard normal variable) is less than \( -2.222 \). This value is approximately \( 0.0132 \). Therefore, the probability that \( X \) is greater than \( 6 \) will be: \[ P(X > 6) = 1 - P(Z < -2.222) \approx 1 - 0.0132 = 0.9868 \] Rounding to the nearest thousandth, the probability that \( X \) is greater than \( 6 \) is: \[ \boxed{0.987} \]