1. + Independent Sample T- test

2. + Welcome! When you get to lab, please pull up the following documents for March 9 th for the Independent Sample T-Test Powerpoint Doc Excel dataset

3. + Difference between Paired Sample T- test and Independent Sample T-Test Paired-sample t-test Pairs of observations Find a correlation, or relationship, between the 2 variables Independent Sample t-test Usually, there are no pairs Completely independent variables

4. + Scenario 1 A previous study done by Illinois State University (2009) showed that students who go to a university that is closer to home tend to visit home more often. Taking this information, conduct an independent sample t-test to determine whether in-state students at Auburn University go home to see their parents more often than out-of-state students. Use an alpha (probability of a Type 1 error, p-level) of.01 What do we know from this scenario? What are our two groups that we are measuring? Is it a one-tailed or two-tailed test? Identify the Independent Variable and its levels

5. + Null/ Research Hypothesis Null Hypothesis: Research Hypothesis:

6. + Statistical decision Based on the results of the t-test, what would your statistical decision be?

7. + Calculating Effect Size 1st: we have to calculate a pooled standard deviation d = (M x – M y ) / s p S p = sqrt (pooled variance) 2 nd : (Mean difference) / s p What does out effect size tell us?

8. + Calculating the Confidence Intervals 1 st : we calculate the pooled standard error: S mp = sqrt (pooled variance/n x + pooled variance/n y ) n x = # of observations of variable 1 n y = # of observations of variable 2 2 nd : we calculate the confidence intervals: Lowerbound = -t crit (s mp ) + Mean difference Upperbound = t crit (s mp ) + Mean difference *Confidence intervals are always two-tailed even if the hypothesis test is one-tailed*

9. + Confidence Intervals Calculate the 99% confidence intervals for the distribution of differences between means. What does this confidence interval tell us?

10. + Practical Decision A company is thinking about creating a bus system for students to travel in-state and they want to know if is worth while. Based on the results of the t-test and what we have found out about the difference between in-state and out-of- state students in relation to going home, would it be practical for this company to create a bus system for in-state students? Use the scenario, statistical test results, effect size, and any additional insights

11. + Your Turn to Practice! Conduct a independent sample t-test to determine if the number of meals eaten at home in a week differs between students living off-campus or on-campus. Use an alpha (error of a Type 1 error, p-level) of.01.