**Lesson 7.5 – Estimating a Mean**

**State and check the Random and Normal/Large Sample conditions for constructing a confidence interval for a population mean.****Determine critical values for calculating a***C*% confidence interval for a population mean.**Calculate a***C*% confidence interval for a population mean.

**Activity: How much does an Oreo weigh?**

Today we’re going to use look at the weights of Oreos to transition from proportions to means. We gave students the mean and standard deviation of the sample to save time, but we did bring in Oreos for the kids. You could have students collect the data themselves. We usually borrow scales from the science teachers when we need to weigh things. Or you could give students data and have them calculate the mean and standard deviation. If you want some sample data, we found this site with data collected by students.

In chapter 6, students learned about the mean and standard deviation of the sampling distribution of a sample mean. They should be able to complete the majority of the activity (#1-5) without teacher input, but you will need to explain that we use table B and *t** instead of table A and *z** for means (#6). We gave students a copy of table B and explained degrees of freedom and then asked them to try to find the critical value needed. After this they can complete the rest of the activity in their groups.