# 8.1.1.2.1 - Example with Summarized Data

## Example: Lactose Intolerance Section

In a sample of 100 African American adults, 70 were identified as having some level of lactose intolerance. Compute a 95% confidence interval to estimate the proportion of all African American adults who have some level of lactose intolerance.

To create a 95% confidence interval of dog ownership using the normal approximation method in Minitab:

In Minitab, select Stat > Basic Statistics > 1-Proportion
1. In this case we have summarized data so select Summarized data in the dropdown.
2. For number of events, add 70 and for number of trials add 100.
3. Select Options
4. The default Confidence level is 95.
5. Change the Method to Normal approximation because the assumption of $$n \widehat p \geq 10$$ and $$n(1- \widehat p) \geq 10$$ has been met
6. Click OK and OK.

This should result in the following output:

#### Method

p: event proportion

Normal approximation is used for this analysis.

Descriptive Statistics
N Event Sample p 95% CI for p
100 70 0.700000 (0.610183, 0.789817)