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 *r*^{2}

*r*^{2} 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.

11. A researcher conducts an independent-measures
study examining 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 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. The data are as follows.
Control
Low Serotonin
n...

1a
The following data were obtained from an independent-measures
research study comparing three treatment conditions.
I
II
III
2
5
7
5
2
3
0
1
6
1
2
4
2
2
T =12
T =10
T =20
G = 42
SS =14
SS =9
SS =10
ΣX2= 182
Use an ANOVA with α = .05 to determine whether there are any
significant mean differences among the treatments.
The null hypothesis in words is
Group of answer choices
a. There...

2) How does the neurotransmitter serotonin influences
aggression? A researcher conducts a study examining how the brain
chemical serotonin is related to aggression. Two samples were
collected; one sample serves as the control group which will not
receive any treatment drug, the second sample receives a drug that
affects serotonin and thus influences aggression. The researcher
finally tests the animals by recording the number of aggressive
responses. The following results were reported:
Treatment group (serotonin
affected):
Control
group:
Rat...

The following data were obtained from an independent-measures
research study comparing three treatment conditions.
I
II
III
n = 6
n = 4
n =
4
M = 2
M = 2.5
M = 5
N = 14
T = 12
T = 10
T = 20
G = 42
SS = 14
SS = 9
SS = 10
ΣX2tot = 182
Use an ANOVA with α = .05 to determine whether there are any
significant mean differences among the...

The following data were obtained from an independent-measures
research study comparing three treatment conditions.
I
II
III
n = 6
n = 4
n =
4
M = 2
M = 2.5
M = 5
N = 14
T = 12
T = 10
T = 20
G = 42
SS = 14
SS = 9
SS = 10
ΣX2tot = 182
Use an ANOVA with α = .05 to determine whether there are any
significant mean differences among the...

1a)
A researcher used a sample of n =16 adults
between the ages of 40 and 45. For each person, the researcher
recorded the difference between the ratings obtained while smiling
and the rating obtained while frowning. On average the cartoons
were rated as funnier when the participants were smiling, with an
average difference of MD = 1.6, with
SS = 135.
Are the cartoons rated as significantly funnier when the
participants are smiling ? Use a one-tailed test with...

An independent-measures research study uses two samples, each
with n = 8 participants. If the data produce a t statistic of t =
2.50, then which of the following is the correct decision for a
two-tailed hypothesis test? Group of answer choices Reject the null
hypothesis with a = .05 but fail to reject with a = .01. cannot
answer without additional information Reject the null hypothesis
with either a = .05 or a = .01. Fail to reject the...

A researcher conducts an independent-measures study examining
the effectiveness of a group exercise program at an assisted living
facility for elderly adults. One group of residents is selected to
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After 6 weeks, the researcher assessed the physical fitness of each
participant. The data are as follows:
Exercise Group: Control Group:
n = 15 n = 10
M = 15.5 M = 12
SS = 190 SS = 120.5...

The following data summarize the results from an independent
measures study comparing three treatment conditions.
I
II
III
n = 6
n = 6
n =
6
M = 4
M = 5
M = 6
N = 18
T = 24
T = 30
T = 36
G = 90
SS = 30
SS = 35
SS = 40
ΣX2tot = 567
Use an ANOVA with α = .05 to determine whether there are
any significant differences among the...

A group of researchers wants to examine whether taking multiple
practice quizzes improve scores on tests. They compare the exam
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