Question 3 - PART A

The head of public safety notices that the average driving speed at a particular intersection averages 35 mph with a standard deviation of 7.5 mph. The head of public safety thinks that putting a school speed limit sign of 20 mph will decrease the speed at the intersection. After a school speed limit sign of 20 mph is placed at the intersection, the first 40 cars travel past at an average speed of 32 mph. Using the .01 significance level, was there a significant change in driving speed? Use the five steps of hypothesis testing. Finally, write your answer as you would for a journal article using APA style.

HYPOTHESIS TESTING

Restate the question as a research hypothesis and a null hypothesis about the populations. Include a description of the two populations.

- Population 1:

- Population 2:

- Research Hypothesis:

- Null Hypothesis:

Determine the characteristics of the comparison distribution.

- M =

- ²M =

- M =

Determine the cutoff sample score (or critical value) on the comparison distribution at which the null hypothesis should be rejected.

- Cutoff =

Determine your sample's score on the comparison distribution.

- Sample's Z-score =

Decide whether to reject the null hypothesis.

Question 3 - PART B

Now we will do the same problem as a two-tailed test.

Step 1: What are the new Research and Null Hypotheses?

Step 2: Remains the same as part A.

Step 3: What is the new cutoff score?

Step 4. Remains the same as part A.

Step 5: What is are decision?

Why are the results different than Part A where we did a one-tailed test?

BONUS: What is the 99% confidence interval?(Note, we only do confidence intervals for two tailed tests).