1. General Homework Comments Final answer for conf. interval or sig. test should be complete sentence in terms of context of problem (e.g., We are 99% confident that the mean healing rate for newts is 25.67  3.1 micrometers per hour.) WORD can insert the symbols µ and , and can do subscripts. Use these features. Hypotheses should be stated symbolically: H 0 : µ = 5 mm, H a : µ  5 mm (for example).

2. Meaning of Significance General Idea: P = probability of observed difference if null hypothesis is true. Large P-value means observed differences could easily occur by chance if null hypothesis is true. Small P-value means that observed difference have small probability of occurring if null hypothesis is true.

3. Meaning of Significance 14.40 The observed difference in polyp occurrence between the two groups was so small that it might reasonably be expected to occur purely by chance if we assumed that diet had no effect. 14.42 While there was some difference in richness and total stem densities between the two areas, those differences were so small that they could easily occur by chance if the population means were identical.

4. Important Ideas from Chapter 15 For statistical inference to be valid, how should the data be produced? What kind of error does the margin of error in a confidence interval account for? What kinds of errors does it not account for? Explain why "statistical significance" is not the same as "practical significance." Give an example. What are Type I and Type II errors?

5. Exam 2—Comments The exam will cover chapters 7-15 (except for chapters 11 and 12). I recommend using the review section beginning on p. 389 (Exercises II.1—II.21, II.24, 25, 30, 31 would be helpful review problems.) You may use a calculator and the formula card insert from your text. You must take the exam at the time scheduled for your section unless you have made prior arrangements with me.