A simple random sample of 85 is drawn from a normally distributed population. The mean is found to be 146, with a standard deviation of 34. Which of the following values is outside the [tex]$99\%$[/tex] confidence interval for the population mean? Use the table below to help you answer the question.

\begin{tabular}{|c|c|c|c|}
\hline
Confidence Level & [tex]$90\%$[/tex] & [tex]$95\%$[/tex] & [tex]$99\%$[/tex] \\
\hline
[tex]$z$[/tex]-score & 1.645 & 1.96 & 2.58 \\
\hline
\end{tabular}

Remember, the margin of error (ME) can be determined using the formula
[tex]\[ ME = \frac{z \cdot s}{\sqrt{n}} \][/tex]

A. The value of 135 because it is not greater than 138.5

B. The value of 137 because it is greater than 136.5

C. The value of 138 because it is less than 153.2

D. The value of 154 because it is greater than 153.2



Answer :

To determine if any of the given values (135, 137, 138, 154) are outside the 99% confidence interval for the population mean, we will follow these steps:

### 1. Determine the Mean and Standard Deviation
- Sample size ([tex]\(n\)[/tex]) = 85
- Sample mean ([tex]\(\bar{x}\)[/tex]) = 146
- Sample standard deviation ([tex]\(s\)[/tex]) = 34
- Z-score for 99% confidence level = 2.58

### 2. Calculate the Margin of Error
The margin of error (ME) can be calculated using the formula:
[tex]\[ ME = z \cdot \frac{s}{\sqrt{n}} \][/tex]

Substituting the values:
[tex]\[ ME = 2.58 \cdot \frac{34}{\sqrt{85}} \][/tex]

This results in a margin of error:
[tex]\[ ME \approx 9.51456987992626 \][/tex]

### 3. Calculate the Confidence Interval
The confidence interval is given by:
[tex]\[ \text{Lower bound} = \bar{x} - ME \][/tex]
[tex]\[ \text{Upper bound} = \bar{x} + ME \][/tex]

Substituting the mean and the margin of error:
[tex]\[ \text{Lower bound} \approx 146 - 9.51456987992626 \][/tex]
[tex]\[ \text{Lower bound} \approx 136.48543012007374 \][/tex]

[tex]\[ \text{Upper bound} \approx 146 + 9.51456987992626 \][/tex]
[tex]\[ \text{Upper bound} \approx 155.51456987992626 \][/tex]

### 4. Check the Given Values
We compare each given value (135, 137, 138, 154) to the bounds of the confidence interval:
- 135: This value is less than the lower bound (136.48543012007374), so it is outside the interval.
- 137: This value is within the interval [tex]\(136.48543012007374 \leq 137 \leq 155.51456987992626\)[/tex].
- 138: This value is within the interval [tex]\(136.48543012007374 \leq 138 \leq 155.51456987992626\)[/tex].
- 154: This value is within the interval [tex]\(136.48543012007374 \leq 154 \leq 155.51456987992626\)[/tex].

### Conclusion
The value 135 is outside the 99% confidence interval for the population mean. Therefore, the value of 135 does not fall within the computed confidence interval and is the correct answer to the given question.