Homework Questions?

Section 9.2Tests about a Population Proportion

Test Statistic• A test statistic measures how far a sample statistic diverges

from what we would expect the null hypothesis we true, in standardized units. That is…

Mr. Suk & Basketball• In a SRS of 50 free throws, Mr. Suk made 32.• What is the test statistic?

• Find and interpret the p-value.

Significance Test• State: What hypotheses do you want to test, and at what

significance level? Define any parameters you use.• Plan: Choose the appropriate inference method. Check

conditions.• Do: If the conditions are met, perform calculations.• Compute the test statistic (z)• Find the P-value

• Conclude: Interpret the results of your test in the context of the problem.

One-Sample z Test for a Proportion

• Find the p-value by calculating the probability of getting a z score this large or larger in the direction specified by

POTATOES again…• If the producer determines that more than 8% of potatoes have

blemishes, the truck will be sent away. A supervisor selects a SRS of 500 potatoes and an inspection reveals that 47 of the potatoes have blemishes. Carry out a significance test at the level. What should the producer conclude?

• State:

• Plan:

• Do:

• Conclude:

POTATOES again…

Two-Sided Tests…Example• A website says that 50% of high school students have never

smoked a cigarette. Trey wonders if this is true in his large, urban high school. Trey selects a SRS of 150 students from his school and 90 of them say they have never smoked a cigarette. What should Trey conclude? Give appropriate evidence to support your answer.

• State:

• Plan:

Trey…• Do:

• Conclude:

How does this tie into confidence intervals?• In Chapter 8 we would have done a confidence interval to be

95% confident…do that for Trey’s school instead!

Homework• Pg 562 (33, 35-38, 46-52, 54-60)• Do 37, 38, and 52 as a class!