Questions: What is the probability that the sample mean score is less than 500 round the answer to at least four decimal places.
The probability that the sample mean score is less than 500 is
assume that a given test mathematics SAT score has a standard deviation was 116. A sample of 65 scores is chosen.
Transcript text: What is the probability that the sample mean score is less than 500 round the answer to at least four decimal places.
The probability that the sample mean score is less than 500 is
assume that a given test mathematics SAT score has a standard deviation was 116. A sample of 65 scores is chosen.
Solution
Solution Steps
Step 1: Define the Problem
We need to find the probability that the sample mean score is less than 500 for a normally distributed population with a mean \( \mu = 500 \) and a standard deviation \( \sigma = 116 \). The sample size is \( n = 65 \).
Step 2: Calculate the Standard Error
The standard error (SE) of the sample mean is calculated using the formula:
\[
SE = \frac{\sigma}{\sqrt{n}} = \frac{116}{\sqrt{65}} \approx 14.3538
\]
Step 3: Determine Z-scores
To find the Z-scores for the bounds, we use the formula:
\[
Z = \frac{X - \mu}{SE}
\]
For the upper bound \( X = 500 \):
\[
Z_{end} = \frac{500 - 500}{14.3538} = 0.0
\]
For the lower bound, which approaches negative infinity:
\[
Z_{start} = -\infty
\]
Step 4: Calculate the Probability
Using the cumulative distribution function \( \Phi \), we find:
\[
P = \Phi(Z_{end}) - \Phi(Z_{start}) = \Phi(0.0) - \Phi(-\infty) = 0.5 - 0 = 0.5
\]
Final Answer
The probability that the sample mean score is less than 500 is
\[
\boxed{P = 0.5}
\]