Instructions:Do you recall the assignment we did a few weeks ago when we calculated the standard deviation and variance for the RBIs for the two baseball teams (for the Washington Nationals and the Houston Astros)? Well, let's revisit those data to figure out if there is a significant difference between the two teams on their RBI records. Here's the data again (note this is the same as the data from your Assignment #6---you might want to look back at that assignment to see your means, SDs, and Variance calculations to save your self some time on this assignment!).

Runs Batted In per Team4

Astros Nationals

80 50

40 63

45 124

100 104

56 56

95 45

56 67

54 50

36 55

6 67

10 40

54 26

5 6

98 45

4 5

14 12

10 10

11 4

12 11

4 4

What is the null hypothesis?

H0: The RBIs of the Nationals is equal to the RBIs of the Astros

H0: The RBIs of the Nationals are better than the RBIs of the Astros

H0: The RBIs of the Astors are better than the RBIs of the Nationals

H0: The RBIs of the Nationals and Astros are significantly different

Select the alternative hypothesis

Ha: The Nationals and Astros have significantly different RBIs

Ha: The Nationals and Astros do not have significantly different RBIs

What is the risk level?

.05

.5

.25

.01

What is the best statistical test to use?

z-test

t-Test for independent samples

t-Test for dependent samples

correlation test

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

t=(m1m2)(((n11)s12+(n21)s22)n1+n22)((n1+n2)n1n2)

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

19

39

38

40

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 assignment---did 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

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

1.56

1.69

2.42

2.02

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

Reject the null hypothesis

Fail to reject the null hypothesis

Not enough information to decide

Write write up results as you would see it in a results section of an empirical research paper Make sure to include the means andSDs for each group. I do NOT need to see the effect size (Cohen's D)

Let's pretend that we got to have a full regular baseball season this year (wouldn't that have been awesome?), and we decided to test whether the teams were different again this season, and we got the following results (written in

An independent samplest-Test comparing two teams on their RBIs in the 2020 season showed a significant difference between these two teamst(38) = 3.379,p< .05. The RBIs for the Nationals (M= 85.95SD= 28.05) was significantly higher than the RBIs for the Astros (M= 56.55 SD = 26.96).

Based on this write up and the means and SDs provided here, calculate the effect size for this new comparison, using the Pooled Variance Formula (Below):

ES=(m1m2)(12+22)2

Group of answer choices

0.12

0.23

1.70

0.43

What "size" is this effect size?

Group of answer choices

Medium

Very Large

Between Medium & Large

Small