Stat 301 – Day 15 Comparing Groups

Statistical Inference Making statements about the “world” based on observing a sample of data, with an indication of your uncertainty How do I “test” a particular value for the parameter of interest?  Statistical significance, p-value  Types of error, power How do I estimate the value of the parameter from the sample data?  Confidence interval  Confidence level

Statistical Investigation Formulate research question Data collection plan Summarize data numerically and graphically (e.g., statistic, bar graph) Statistical inference if appropriate  Representative sample from process, large population  Simulation, “Exact” methods, normal approximations Summarize conclusions in context  Generalizability

Investigation 2.1: Teen Hearing Loss

The Big Picture Want to compare two groups Simulate the sampling process under the null hypothesis that the population proportions are equal How extreme is our observed difference in sample proportions under this null hypothesis (by random sampling alone)? If p-value is small, have convincing evidence of a difference in the population proportions

To Do Submit project in PolyLearn!  One team member Practice problem 2.1A (p. 98) Complete questions a-c of Investigation 2.2 Fun video Start HW 4!

Exam 1 Solutions to be posted in PolyLearn  See me with grading questions Mean:.82 (Median:.83, Max:.94)  Overall grade updating in PolyLearn Skills to continue to improve  Hard to convince me of two-sided in 1b  What is meant by “simulation”  How check validity of a test procedure  Use random sampling as justification to generalize  Interpretation vs. evaluation  Dangers of multiple testing