True or False: A sample size of 36 provides a sample mean of 10. If the population variance is known to be 16 and the population distribution is assumed to be normal, the lower limit for a 99% confidence interval is 11.7173.

1 answer

To determine whether the statement is true or false, we need to calculate the 99% confidence interval for the sample mean using the given information.

  1. Sample Size (n): 36
  2. Sample Mean (\( \bar{x} \)): 10
  3. Population Variance (\( \sigma^2 \)): 16
  4. Population Standard Deviation (\( \sigma \)): \( \sqrt{16} = 4 \)
  5. Confidence Level: 99%

First, we need to calculate the critical z-value for a 99% confidence level. The z-value for a two-tailed confidence level of 99% is approximately 2.576.

Next, we calculate the standard error (SE) of the mean:

\[ SE = \frac{\sigma}{\sqrt{n}} = \frac{4}{\sqrt{36}} = \frac{4}{6} = \frac{2}{3} \approx 0.6667 \]

Now we can calculate the margin of error (ME):

\[ ME = z \cdot SE = 2.576 \cdot 0.6667 \approx 1.718 \]

Now we can determine the confidence interval. The sample mean is 10, so we will calculate the lower and upper limits:

  • Lower Limit:

\[ \text{Lower Limit} = \bar{x} - ME = 10 - 1.718 \approx 8.282 \]

  • Upper Limit:

\[ \text{Upper Limit} = \bar{x} + ME = 10 + 1.718 \approx 11.718 \]

Thus, the 99% confidence interval for the sample mean is approximately (8.282, 11.718).

The statement claims that the lower limit of the 99% confidence interval is 11.7173, which is incorrect. The lower limit we calculated is approximately 8.282, not 11.7173.

Therefore, the statement is False.