Use the confidence level and sample data to find a confidence interval for estimating the population µ.
-A random sample of 79 light bulbs had a mean life of $x = 400$ hours with a standard deviation of $\sigma = 28$ hours. Construct a 90 percent confidence interval for the mean life, $\mu$, of all light bulbs of this type.
A) $393

Question

Use the confidence level and sample data to find a confidence interval for estimating the population µ.
-A random sample of 79 light bulbs had a mean life of $x = 400$ hours with a standard deviation of $\sigma = 28$ hours. Construct a 90 percent confidence interval for the mean life, $\mu$, of all light bulbs of this type.
A) $393 < \mu < 407$
B) $394 < \mu < 406$
C) $395 < \mu < 405$
D) $392 < \mu < 408$

Quizplus · Accepted Answer

The 90% confidence interval is calculated using the formula: $\bar{x} \pm z \times \frac{\sigma}{\sqrt{n}}$. For 90% confidence, $z \approx 1.645$. Thus, $400 \pm 1.645 \times \frac{28}{\sqrt{79}}$ gives the interval $395 < \mu < 405$.

Use the Confidence Level and Sample Data to Find a Confidence