A company claims that the mean monthly residential electricity consumption in a certain region is more than 860 kiloWatt-hours (kWh). You want to test this claim. You find that a random sample of 66 residential cust mean monthly consumption of 900 kWh. Assume the population standard deviation is 123 kWh. At a= 0.10, can you support the claim? Complete parts (a) through (e) B. The critical value is 1.28 Identify the rejection region(s). Select the correct choice below. O A. The rejection regions are z< -1.28 and z> 1.28. YB. The rejection region is z> 1.28 OC. The rejection region is z <1.28. (c) Find the standardized test statistic. Use technology. The standardized test statistic is z=

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**Hypothesis Testing Example**

**Scenario:**
A company claims that the mean monthly residential electricity consumption in a certain region exceeds 860 kiloWatt-hours (kWh). You want to test this claim. You have a random sample of 66 residential customers, with a mean monthly consumption of 900 kWh. Assume the population standard deviation is 123 kWh. With a significance level (\( \alpha \)) of 0.10, can you support the claim? Follow steps (a) through (e).

**(a) Critical Value:**
- **Chosen Option:** B. The critical value is 1.28

**(b) Identify the Rejection Region(s):**
- **Chosen Option:** B. The rejection region is \( z > 1.28 \)

**(c) Standardized Test Statistic:**
- The standardized test statistic \( z \) needs to be calculated.
- The problem prompt instructs rounding the value to two decimal places once computed.
  
To solve this, use the formula for the standardized test statistic:

\[
z = \frac{\bar{x} - \mu}{\frac{\sigma}{\sqrt{n}}}
\]

Where:
- \( \bar{x} = 900 \) (sample mean)
- \( \mu = 860 \) (population mean under the null hypothesis)
- \( \sigma = 123 \) (population standard deviation)
- \( n = 66 \) (sample size)

Compute the test statistic to decide whether to reject the null hypothesis in favor of the alternative claim that the mean consumption is indeed greater than 860 kWh.
Transcribed Image Text:**Hypothesis Testing Example** **Scenario:** A company claims that the mean monthly residential electricity consumption in a certain region exceeds 860 kiloWatt-hours (kWh). You want to test this claim. You have a random sample of 66 residential customers, with a mean monthly consumption of 900 kWh. Assume the population standard deviation is 123 kWh. With a significance level (\( \alpha \)) of 0.10, can you support the claim? Follow steps (a) through (e). **(a) Critical Value:** - **Chosen Option:** B. The critical value is 1.28 **(b) Identify the Rejection Region(s):** - **Chosen Option:** B. The rejection region is \( z > 1.28 \) **(c) Standardized Test Statistic:** - The standardized test statistic \( z \) needs to be calculated. - The problem prompt instructs rounding the value to two decimal places once computed. To solve this, use the formula for the standardized test statistic: \[ z = \frac{\bar{x} - \mu}{\frac{\sigma}{\sqrt{n}}} \] Where: - \( \bar{x} = 900 \) (sample mean) - \( \mu = 860 \) (population mean under the null hypothesis) - \( \sigma = 123 \) (population standard deviation) - \( n = 66 \) (sample size) Compute the test statistic to decide whether to reject the null hypothesis in favor of the alternative claim that the mean consumption is indeed greater than 860 kWh.
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