Confidence Interval 26Ff95
1. **State the problem:** We want to find a 90% confidence interval for the mean weekend customer spend amount at Forest City Casino based on the given sample data.
2. **Identify the type of problem:** Since we are estimating the average amount spent (a numerical value), this is a problem involving the **mean**.
3. **Formula for confidence interval for the mean:**
$$\text{CI} = \bar{x} \pm t^* \times \frac{s}{\sqrt{n}}$$
where:
- $\bar{x}$ is the sample mean
- $s$ is the sample standard deviation
- $n$ is the sample size
- $t^*$ is the critical value from the t-distribution for 90% confidence and $n-1$ degrees of freedom
4. **Calculate sample size $n$:** Count the number of data points. There are 150 data points.
5. **Calculate sample mean $\bar{x}$:** Sum all values and divide by 150.
6. **Calculate sample standard deviation $s$:** Use the formula
$$s = \sqrt{\frac{1}{n-1} \sum_{i=1}^n (x_i - \bar{x})^2}$$
7. **Find $t^*$ value:** For 90% confidence and $df = 149$, $t^* \approx 1.655$ (from t-tables or software).
8. **Compute margin of error:**
$$\text{ME} = t^* \times \frac{s}{\sqrt{n}}$$
9. **Calculate confidence interval:**
$$\text{Lower bound} = \bar{x} - \text{ME}$$
$$\text{Upper bound} = \bar{x} + \text{ME}$$
10. **Perform calculations with the data:**
- Sum of all spends $= 83075$
- Sample mean $\bar{x} = \frac{83075}{150} = 553.83$
- Sample standard deviation $s \approx 1703.44$
- Margin of error $= 1.655 \times \frac{1703.44}{\sqrt{150}} \approx 229.88$
11. **Final 90% confidence interval:**
$$553.83 - 229.88 = 323.95$$
$$553.83 + 229.88 = 783.71$$
**Interpretation:** We are 90% confident that the true mean weekend customer spend amount is between $323.95 and $783.71.
**Answers:**
- Blank #1: MEAN
- Blank #2: 323.95
- Blank #3: 783.71