Inference for a Population Mean Review

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.

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

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

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.

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?

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

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.