Week 7 Chapter 6 - Introduction to Inferential Statistics: Sampling and the Sampling Distribution & Chapter 7 – Estimation Procedures

Chapter 6 Introduction to Inferential Statistics: Sampling and the Sampling Distribution

In This Presentation The basic logic of hypothesis testing Hypothesis testing for single sample means or proportions The Five-Step Model Other material covered: One- vs. Two- tailed tests Type I vs. Type II error Student’s t distribution

Applying Logic and Terminology Population = All 20,000 students. Sample = The 500 students selected and interviewed. Statistic =74% (% of sample that held a job during the semester). Parameter = % of all students in the population who held a job.

Three Distributions

Chapter 7 Estimation Procedures

Interval Estimation Procedures 1. Set the alpha (α), probability that the interval will be wrong 2. Find the Z score associated with alpha using Appendix A 3. Substitute values into appropriate equation 4. Interpret the interval Additional consideration: If the Z score you are seeking is between two other scores, choose the larger of the two Z scores

Interval Estimation Procedures Finding Z Setting alpha equal to 0.05 produces a 95% confidence level and means the researcher is willing to be wrong 5% of the time If alpha is equal to 0.05, we would place half (0.025) of this probability in the lower tail and half in the upper tail of the distribution Looking up this area in column c of Appendix A, we find a Z of 1.96

Interval Estimation Procedures Finding Z

Interval Estimation Procedures Finding Z for Common Confidence Levels

Interval Estimation Procedures