1. Inference for a Population Mean
Review

2. How do sample means vary?
According to a bell curve
The average of the sample means is the population mean
The standard deviation is the population standard deviation divided by the square root of the sample size.

3. Two types of inference
Confidence Interval – Used to estimate a population mean.
Hypothesis test – Used to test a claim about the population mean.

4. Confidence Interval Formula to Estimate a Population Mean
If the population standard deviation is known or the sample size is large:
If the population standard deviation is not known and the sample size is less than 30

5. Hypothesis Test to Test a Population Mean
Null Hypothesis:
Collect a random sample and compute a sample mean and standard deviation.
Compute the t-test statistic
Find the p-value
State your conclusions.

6. Looking Ahead
Is there any association between gender and the amount of time one exercises per week?
Is there any association between the model of SUV’s and highway gas mileage?

7. Correlation
Both examples involve investigating correlation between a CATEGORICAL and a NUMERIC variable.
Recall the appropriate test in this situation is ANOVA.

8. Section 7.3
Understanding the Difference Between Sample Variability and Within Sample Variability
We’ll use an example involving highway m.p.g. of various models of trucks to motivate this topic.