An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 45 bulbs has an average life of 710 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm. Click here to view page 1 of the standard normal distribution table. Click here to view page 2 of the standard normal distribution table. Click here to view page 1 of the table of critical values of the t-distribution. Click here to view page 2 of the table of critical values of the t-distribution. The confidence interval is |<µ<

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### Problem Statement

An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 45 bulbs has an average life of 710 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm.

- Click here to view page 1 of the standard normal distribution table.
- Click here to view page 2 of the standard normal distribution table.
- Click here to view page 1 of the table of critical values of the t-distribution.
- Click here to view page 2 of the table of critical values of the t-distribution.

### Solution

The confidence interval is [ ___ ] < μ < [ ___ ].

(Round to the nearest integer as needed.)
Transcribed Image Text:### Problem Statement An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 45 bulbs has an average life of 710 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm. - Click here to view page 1 of the standard normal distribution table. - Click here to view page 2 of the standard normal distribution table. - Click here to view page 1 of the table of critical values of the t-distribution. - Click here to view page 2 of the table of critical values of the t-distribution. ### Solution The confidence interval is [ ___ ] < μ < [ ___ ]. (Round to the nearest integer as needed.)
**Determining Sample Size for Confidence in Mean Lifespan of Light Bulbs**

An electrical firm manufactures light bulbs that have a lifespan approximately normally distributed with a standard deviation of 40 hours. To ensure the sample mean is within 14 hours of the true mean with 94% confidence, calculate the necessary sample size.

- [View page 1 of the standard normal distribution table](#)
- [View page 2 of the standard normal distribution table](#)
- [View page 1 of the table of critical values of the t-distribution](#)
- [View page 2 of the table of critical values of the t-distribution](#)

---

**Solution:**

The required sample size is [ _ ].  
(Note: Round up to the nearest whole number as needed.)
Transcribed Image Text:**Determining Sample Size for Confidence in Mean Lifespan of Light Bulbs** An electrical firm manufactures light bulbs that have a lifespan approximately normally distributed with a standard deviation of 40 hours. To ensure the sample mean is within 14 hours of the true mean with 94% confidence, calculate the necessary sample size. - [View page 1 of the standard normal distribution table](#) - [View page 2 of the standard normal distribution table](#) - [View page 1 of the table of critical values of the t-distribution](#) - [View page 2 of the table of critical values of the t-distribution](#) --- **Solution:** The required sample size is [ _ ]. (Note: Round up to the nearest whole number as needed.)
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