Instructions: recall the assignment we did a few weeks ago when we calculated the standard deviation and variance for the batting averages of 15 players on two baseball teams? Well, let's revisit those data to figure out if there is a significant difference between the two teams. Our goal is to test if they are significantly different. (note this is the same as the data from your Assignment #6you might want to look back at that assignment to see your means, SDs, and Variance calculations to save yourself some time on this assignment!).

Batting Averages for 15 LA Dodgers Players Batting Averages for 15 Houston Astros Players

0.249 0.277

0.278 0.278

0.258 0.294

0.264 0.279

0.297 0.319

0.254 0.257

0.306 0.27

0.254 0.172

0.165 0.311

0.338 0.235

0.27 0.259

0.242 0.26

0.215 0.211

0.215 0.304

0.169 0.176

1. What is the null hypothesis?
2. What is the alternative hypothesis?
3. What is the risk level?

Group of answer choices

.25

.05

.01

.5

4- What is the best statistical test to use?

Group of answer choices

ANOVA

t-Test for dependent samples

z-test

t-Test for independent samples

correlation test

5- Compute the test statistic. The formula is below for you. Also, remember to use the variance rather than the standard deviation in your calculation. You have already calculated the variance for your previous assignment, so that part is already done! Put your calculated t value below, round your answer to two decimal places:

6- Now it's time to compare our obtained value (the one you just calculated) to the critical value. First, we'll need the degrees of freedom. What are the degrees of freedom?

Group of answer choices

40

19

39

28

7- Should we use a "one tailed" or a "two tailed" test for this?

Hint: To figure this out, think about whether it is directional or non-directional. Take a look at your alternative hypothesis (above!), and think about the prompt for the assignmentdid we expect a specific team to be better than the other (directional), or are we simply looking at whether the teams are different (non-directional)?

Group of answer choices

two tailed

one tailed

8- What is the critical value for this statistical test? (hint: you'll need your answers to the previous two questions, as well as your "level of risk"; remember, if the exact degrees of freedom aren't in the t-test table of critical values, you can choose the closest value that is there).

Group of answer choices

1.701

1.562

2.049

2.023

9- Write up your results as you would see it in a results section of an empirical research paper (in APA style). Make sure to include the means and SDs.

10- Based on your answer to the previous question, what is your decision?

Group of answer choices

Fail to reject the null hypothesis

Not enough information to decide

Reject the null hypothesis

11- Imagine that you also want to compare two other teams, The Red Sox and Yankees. After do anther t-test to compare the two teams and you writ the following write-up:

An independent samples t-Test comparing the average batting averages of the Red Sox and Yankees was significant, t(28) = 1.92, p < .05. The batting average for the Red Sox was significantly higher (M = 0.25, SD = 0.05) than the batting average for the Yankees (M = 0.210, SD = .05).

Calculate the effect size for this new t-test, using the Pooled Variance Formula (Below). Round your answer to two decimal places.

12- What "size" is this effect size?

Group of answer choices

Medium

There isn't enough information to answer this question.

Large

Small