1. Stat 301 – Day 37 Bootstrapping, cont (5.5)

2. Last Time - Bootstrapping A simulation tool for exploring the sampling distribution of a statistic, using only the information in the obtained sample!  In particular, standard error of the statistic Median, “trimmed mean,” (heart transplant data)…  Confidence interval: statistic + t  SE(statistic)  95% Percentile CI:  No “technical conditions” other than random sample!

3. Two samples? Investigation 5.5.1 (p. 454) Transplants.mtw What was random in this study?  Independent random samples from two populations?  Random assignment to treatment groups?

4. Investigation 5.5.1 (d) Treat as random samples but consider the difference in medians Bootstrap each sample, calculate difference in medians How would you describe this distribution? Percentile confidence interval (f-h) Observed difference statistically significant?

5. Investigation 5.5.1 (j) Treat as randomly assigned groups How would you describe this distribution? Observed difference statistically significant? Confidence interval?

6. HW Note Exercise #42: Should really be using randomization distribution but go ahead in use bootstrap samples for fish oil and control groups

7. For Thursday Finish HW 8? Schematic of (most common) statistical procedures Examples 5.1, 5.2; chapter summary; technology summary