\( X \) is a normally distributed random variable with mean 7 and standard deviation 22 . What is the probability that \( X \) is between 51 and 73 ? Use the \( 0.68-0.95-0.997 \) rule and write your answer as a decimal. Round to the nearest thousandth if necessary.
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To find the probability that \( X \) is between 51 and 73 for a normally distributed random variable with mean 7 and standard deviation 22, we first calculate the z-scores for 51 and 73. The z-score is calculated as: \[ z = \frac{X - \mu}{\sigma} \] For \( X = 51 \): \[ z = \frac{51 - 7}{22} = \frac{44}{22} = 2 \] For \( X = 73 \): \[ z = \frac{73 - 7}{22} = \frac{66}{22} = 3 \] Now we need to look up the z-scores in a standard normal distribution table or use the \( 0.68-0.95-0.997 \) rule. A z-score of 2 corresponds to approximately 97.5% probability, and a z-score of 3 corresponds to approximately 99.85% probability. Now, we find the probability that \( X \) is between 51 and 73: \[ P(51 < X < 73) = P(Z < 3) - P(Z < 2) \] \[ = 0.9985 - 0.975 = 0.0235 \] Thus, the probability that \( X \) is between 51 and 73 is approximately **0.024** when rounded to the nearest thousandth.