Question

1a)

A researcher conducts an independent-measures study to examine how the brain chemical serotonin is related to aggression. One sample of rats serves as a control group and receives a placebo that does not affect normal levels of serotonin. A second sample of rats, low serotonin group, receives a drug that lowers brain levels of serotonin. Then, the researcher tests the animals by recording the number of aggressive responses each of the rats display. See the data below. Is there a significant difference between the control group and the low serotonin group regarding the number of aggressive responses?

                                               Control         Low Serotonin  

                                                 n = 10                 n = 15

                                               M = 14               M = 19

                                               SS = 180.5       SS = 130

Perform a hypothesis test using independent-measures t-test. Use a two-tailed test with α = .05, and answer the following questions.

You will be using a independent-measures t-test because ___________________

Select all the correct answers

Group of answer choices

a. You do not know the population mean and population standard deviation

b. You are using data from a single sample

c. You are comparing the means of two different samples

d. you can use either independent-measures or repeated-measures t test

e. You know the population standard deviation, but not the population mean

f. You know the population mean, but not the population standard deviation

1b)

The null hypothesis in words is

Group of answer choices

a. The low serotonin group exhibits a greater number of aggressive responses than the control group

b. There is a significant difference between the control group and the low serotonin group regarding the number of aggressive responses

c. The low serotonin group does not exhibit a greater number of aggressive responses than the control group

d. There is not a significant difference between the control group and the low serotonin group regarding the number of aggressive responses

1c)

The alternative hypothesis in symbols is

Group of answer choices

a. H1: µ low serotonin ≠ µ control

b. H1: µ low serotonin ≤ µ control

c. H1: µ low serotonin = µ control

d. H1: µ low serotonin > µ control

1d)

The critical t values are

Group of answer choices

a. ±1.714

b. ±2.807

c. .685

d. ±2.069

1e)

The t-statistic is

1f)

Your decision is

Group of answer choices

Fail to reject the null hypothesis and conclude that there is a significant difference between the control group and the low serotonin group regarding the number of aggressive responses

Reject the null hypothesis and conclude that there is not a significant difference between the control group and the low serotonin group regarding the number of aggressive responses

Fail to reject the null hypothesis and conclude that there is not a significant difference between the control group and the low serotonin group regarding the number of aggressive responses

Reject the null hypothesis and conclude that there is a significant difference between the control group and the low serotonin group regarding the number of aggressive responses

1g)

Compute r²

r² is

Answer 1

You will be using a independent-measures t-test because

a. You do not know the population mean and population standard deviation

c. You are comparing the means of two different samples

1b) The null hypothesis in words is

c. There is not a significant difference between the control group and the low serotonin group regarding the number of aggressive responses

1c)

a. H1: µ low serotonin ≠ µ control

1d)

The critical t values are

d. ±2.069

1e)

The t-statistic is

1f)

Fail to reject the null hypothesis and conclude that there is not a significant difference between the control group and the low serotonin group regarding the number of aggressive responses.