1. **State the problem:** We have a random sample of 15 standardized test scores with a sum of 1042. We want to find the mean and sample standard deviation, then use the normal distribution and empirical rule to estimate a 95% confidence interval for the true population mean.
2. **Calculate the sample mean:** The sample mean $\bar{x}$ is given by
$$\bar{x} = \frac{\text{sum of samples}}{\text{number of samples}} = \frac{1042}{15} = 69.4667 \approx 69.5$$
3. **Sample standard deviation:** Since the problem states to use a statistics calculator, assume the sample standard deviation $s$ is calculated from the sample data. (If not given, it cannot be computed exactly here.)
4. **Empirical rule and confidence interval:** For a 95% confidence interval using the normal distribution, the interval is approximately
$$\bar{x} \pm 2 \times \frac{s}{\sqrt{n}}$$
where $n=15$ is the sample size.
5. **Summary:**
- Sample mean $\bar{x} = 69.5$
- Sample standard deviation $s$ (from calculator)
- Margin of error $= 2 \times \frac{s}{\sqrt{15}}$
6. **Final 95% confidence interval:**
$$\left(69.5 - 2 \times \frac{s}{\sqrt{15}},\ 69.5 + 2 \times \frac{s}{\sqrt{15}}\right)$$
Round the interval endpoints to the nearest tenth once $s$ is known.
**Note:** Without the exact sample standard deviation value, the numeric interval cannot be completed here.
Confidence Interval 63Bdcb
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.