Your professor wants to determine if her students today are performing better in statistics than 10 years ago. End of semester grades from a random sample of students enrolled today and one of students enrolled 10 years ago have been obtained: Today 10 Years Ago 82 88 112.5 54 o2 45 36 n Refer to Exhibit GGC 2-2. The test statistic for the difference between the two population means is a) -47 b) -.65 c) -3 d) -1.5

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### Statistical Performance Comparison Over Time

Your professor wants to determine if her students today are performing better in statistics than 10 years ago. End of semester grades from a random sample of students enrolled today and one of students enrolled 10 years ago have been obtained:

|                | Today | 10 Years Ago |
|----------------|-------|--------------|
| Mean (\( \bar{x} \))  | 82    | 88           |
| Variance (\( \sigma^2 \)) | 112.5 | 54           |
| Sample Size (\( n \))    | 45    | 36           |

Refer to Exhibit GGC 2-2. The test statistic for the difference between the two population means is ____.

**Options:**
- a) \(-.47\)
- b) \(-.65\)
- c) \(-3\)
- d) \(-1.5\)

### Explanation
To find the test statistic for the differences between the two means, use the formula for the two-sample Z-test:

\[
Z = \frac{(\bar{x}_1 - \bar{x}_2)}{\sqrt{\frac{\sigma_1^2}{n_1} + \frac{\sigma_2^2}{n_2}}}
\]

Where:
- \( \bar{x}_1 \) and \( \bar{x}_2 \) are the sample means
- \( \sigma_1^2 \) and \( \sigma_2^2 \) are the sample variances
- \( n_1 \) and \( n_2 \) are the sample sizes

Substitute in the given values to calculate the Z value and select the correct option.
Transcribed Image Text:### Statistical Performance Comparison Over Time Your professor wants to determine if her students today are performing better in statistics than 10 years ago. End of semester grades from a random sample of students enrolled today and one of students enrolled 10 years ago have been obtained: | | Today | 10 Years Ago | |----------------|-------|--------------| | Mean (\( \bar{x} \)) | 82 | 88 | | Variance (\( \sigma^2 \)) | 112.5 | 54 | | Sample Size (\( n \)) | 45 | 36 | Refer to Exhibit GGC 2-2. The test statistic for the difference between the two population means is ____. **Options:** - a) \(-.47\) - b) \(-.65\) - c) \(-3\) - d) \(-1.5\) ### Explanation To find the test statistic for the differences between the two means, use the formula for the two-sample Z-test: \[ Z = \frac{(\bar{x}_1 - \bar{x}_2)}{\sqrt{\frac{\sigma_1^2}{n_1} + \frac{\sigma_2^2}{n_2}}} \] Where: - \( \bar{x}_1 \) and \( \bar{x}_2 \) are the sample means - \( \sigma_1^2 \) and \( \sigma_2^2 \) are the sample variances - \( n_1 \) and \( n_2 \) are the sample sizes Substitute in the given values to calculate the Z value and select the correct option.
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