PSYCH248 - STATISTICS

Computer Lab Assignment II, Summer 2021 Comparing means using t-tests

This assignment will give you practice choosing the appropriate test statistic to use for different research designs that all involve comparing means using t-tests.You will need to enter the data, use JASP to test the hypothesis, and conclusion for each problem stating whether the samples differed significantly. Select the type of test and the variables.

Problem 1: Depression and anxiety

Depression is a serious mental disorder that has been shown to respond very well to cognitive therapy. You want to test the effectiveness of cognitive therapy on a group of people suffering from anxiety. You select a random sample of 15 people diagnosed with anxiety disorder and treat them with cognitive therapy.

The following are the scores for the sample: 4, 3, 6, 2, 4, 6, 7, 5, 2, 1, 8, 9, 7, 4, and 10. Higher scores indicate more anxiety. Three times previously you administered a Likert-type scale, as a test of anxiety, and found there was an average score 6 points.

Independent variable: ____________________ Dependent variable: _________________

State Mathematical Hypotheses: H₀: _________________H₁: ____________________

Hypotheses in words. H₀: ______________________________________________________ _

H₁: _______________________________________________________________________ __

What is the proper t-test? __ _________.One-tailed or two-tailed? ______________________

Problem 2: Oxygen consumption and music

The amount of oxygen consumption was measured in six individuals, over two 10-minute periods, while they were sitting with their eyes closed. During one period, they listened to an exciting adventure story, during the other, they heard restful music.

Participant Story Music

D2

1 5.00 4.00

2 7.25 6.75

3. 5.50 4.75

4 6.25 5.00

5 5.50 6.00

6 6.50 6.00

7 7.75 6.50

8 5.00 5.75

9 6.00 6.75

10 6.00 4.50

=

Based on the results obtained, does listening to music lower oxygen consumption? Test hypothesis at .05 significance level. Calculate by hand, and JASP; INCLUDE SUMMARY PRINTOUT(S).

Hypothesis:

H₀: ______________________________________________________________________

H₁: _______________________________________________________________________

Degrees of freedom (df): _____________. Critical value: ___________

M_D: _______. SS_D: ____ ____. s²: ________. S_MD: _________. t = _________

Using the variables of the study, report findings

Problem 3: Expressive writing and physical health

A team of researchers is interested in the effect on physical health of writing about thoughts and feelings associated with traumatic life events (expressive writing). The researchers recruit 30 undergraduate students to take part in the study and randomly assign them to be in an expressive writing group or a control group. Students in the expressive writing group are instructed to write four 20 - minute essays over four consecutive days about their most traumatic life experiences. Students in the control group write four 20 - minute essays over consecutive days describing their plans for that day. One week later, the researchers ask the students to rate their overall level of physical health (on a scale 0 = very poor health, to 100 = perfect health).

EWG: 75, 86, 77, 91, 68, 74, 62, 93, 82, 79, 94, 56, 79, 86, 90, 97

CWG: 81, 76, 71, 70, 62, 50, 58, 63, 76, 64, 65, 72, 52, 59

The researchers were interested in identifying a positive or a negative health effect of expressive writing. Run the proper t test to see if this previous research is supported.

Independent variable:

Dependent variable:

Statistical Hypotheses: H₀:__ __________________H₁:______________________

State Hypotheses in words:

H₀: __________________________________________________________________________

H₁: _________________________________________________________________________ _

Proper t-test: ___________________ One-tailed or two-tailed? _ ___________

Was the data normally distributed? Were the variances of the two groups significantly different from each other? What does that mean?