short term memory and marijuana/LAB 7/ Begin by opening the “Lab 7 Data.sav” file

short term memory and marijuana/LAB 7/ Begin by opening the “Lab 7 Data.sav” file
As you look at the data … recognize that the data matrix represents a 2 x 2 factorial representation…but we can think of the data as representing several different design configurations

Step 1. Begin by changing the name of the variable VAR.Dep.01 – this is a dependent variable you should associate with their own primary dependent variable of interest…you should change that name to represent your variable of interest

Step 2. Select the Analyze drop down menu from the top Tool Bar

1. go to “Descriptive Statistics” and select “Frequencies”
a) select the dependent variable that you have just renamed and either select “Paste” or “OK”
b) “Pasted” selections must of course be executed from the Syntax window
2. Look at the Output and discuss the frequency table in terms of your own “imagined” variable
3. Go to the Graphs drop down menu and select a “Histogram” graph so you can confirm your thoughts
You may want to examine other aspects of Descriptive statistics as well – e.g. “Descriptives”

Step 3. Select the Analyze drop down menu from the top Tool Bar

1. go to “Compare Means” and select “One Sample t-test”
a) This is a test of a hypothesized mean (a parameter of the population, not a statistic of your sample) that a group is expected to obtain and not a comparison between groups
b) thus, there is no grouping to consider, the data is imagined to be data collected on one group
c) select the dependent variable that you have renamed and identify the value that you want to test
d) Look at the Output and discuss the results in terms of your own “imagined” variable

2. What does the output suggest?

3. Especially note whether the 95% confidence interval does – or – does not include zero … relate this fact to the Sig(2-tailed) value – if there is NO DIFFERENCE between your sample mean and your hypothesized population mean, then the 95% confidence interval will include zero; but if there IS a difference between your sample mean and your hypothesized population mean, then the 95% confidence interval will NOT include zero;” Depending on your hypothesized population mean, your sample mean may OR may not be different from your hypothesized mean.
4. Summarize the Results… identify your imagined variable and identify the hypothesized mean that you were predicting. Identify your conclusion about whether they are different or not.
The imagined dependent variable is short-term memory. The hypothesized mean for short-term memory predicted on the one sample t-test is 3.54.

Step 4. Now consider a “simple” experiment, where there are two levels to the independent variable…again, imagine the different levels.

Go to the Variable View and change the name of VAR.Gpr.01 to represent some abbreviation of your IV manipulation…also click on “Values” and name the levels of the independent variable

Notice the “dummy coding” in the SPSS matrix with respect to the nominal grouping procedure

Again, Select the Analyze drop down menu from the top Tool Bar

1. go to “Compare Means” and select “Independent Samples t-test”
2. select the dependent variable that you have been working with and then select the grouping variable that you have just renamed / then define the groups (1 & 2)…also, note that the options allows you to change your alpha level
3. Run – or – paste and run your analysis
4. Report the results

Group Statistics
Marijuana.dosage N Mean Std. Deviation Std. Error Mean
short.term.memory THC 100 3.29 2.226 .223
CBD 100 3.79 2.606 .261
Independent Samples Test
Levene’s Test for Equality of Variances t-test for Equality of Means
F Sig. t df Sig. (2-tailed) Mean Difference Std. Error Difference 95% Confidence Interval of the Difference
Lower Upper
short.term.
memory Equal variances assumed 2.529 .113 -1.459 198 .146 -.500 .343 -1.176 .176
Equal variances not assumed -1.459 193.268 .146 -.500 .343 -1.176 .176

Step 5. Now consider a 2 x 2 factorial design, where there are two levels to two independent variables…again, imagine the new IV or quasi-IV and the different levels to that IV. Again, Rename the IV and identifying the levels in Variable View…inspect the coding scheme, noting how the coding identifies the cells of the factorial matrix
Again, Select the Analyze drop down menu from the top Tool Bar

1. go to “General Linear Model” and select “Univariate”
2. Select the dependent variable you have been discussing and select the two independent variable you have identified
3. Select “Plots” and identify the axes that you wish to plot the independent effects on
4. Run – or – paste and run your analysis
5. Report the results
Submit on your work on Blackboard.
Statistics
short.term.memory
N Valid 200
Missing 0
short.term.memory
Frequency Percent Valid Percent Cumulative Percent
Valid 0 22 11.0 11.0 11.0
1 26 13.0 13.0 24.0
2 22 11.0 11.0 35.0
3 35 17.5 17.5 52.5
4 30 15.0 15.0 67.5
5 27 13.5 13.5 81.0
6 13 6.5 6.5 87.5
7 10 5.0 5.0 92.5
8 9 4.5 4.5 97.0
9 3 1.5 1.5 98.5
10 2 1.0 1.0 99.5
11 1 .5 .5 100.0
Total 200 100.0 100.0

T-TEST
/TESTVAL=0
/MISSING=ANALYSIS
/VARIABLES=short.term.memory
/CRITERIA=CI(.95).

T-test
One-Sample Statistics
N Mean Std. Deviation Std. Error Mean
short.term.memory 200 3.54 2.431 .172

One-Sample Test
Test Value = 0
t df Sig. (2-tailed) Mean Difference 95% Confidence Interval of the Difference
Lower Upper
short.term.memory 20.597 199 .000 3.540 3.20 3.88

Descriptive Statistics
N Minimum Maximum Mean Std. Deviation
short.term.memory 200 0 11 3.54 2.431
Valid N (listwise) 200

T-TEST GROUPS=Marijuana.dosage(1 2)
/MISSING=ANALYSIS
/VARIABLES=short.term.memory
/CRITERIA=CI(.95).

Group Statistics
Marijuana.dosage N Mean Std. Deviation Std. Error Mean
short.term.memory THC 100 3.29 2.226 .223
CBD 100 3.79 2.606 .261

Independent Samples Test
Levene’s Test for Equality of Variances t-test for Equality of Means
F Sig. t df Sig. (2-tailed) Mean Difference Std. Error Difference 95% Confidence Interval of the Difference
Lower Upper
short.term.memory Equal variances assumed 2.529 .113 -1.459 198 .146 -.500 .343 -1.176 .176
Equal variances not assumed -1.459 193.268 .146 -.500 .343 -1.176 .176

T-TEST GROUPS=Marijuana.dosage(1 2)
/MISSING=ANALYSIS
/VARIABLES=Drug.history
/CRITERIA=CI(.95).
UNIANOVA short.term.memory BY Marijuana.dosage Drug.history
/METHOD=SSTYPE(3)
/INTERCEPT=INCLUDE
/PLOT=PROFILE(Marijuana.dosage Drug.history)
/CRITERIA=ALPHA(0.05)
/DESIGN=Marijuana.dosage Drug.history Marijuana.dosage*Drug.history.
Univariate Analysis of Variance

Between-Subjects Factors
Value Label N
Marijuana.dosage 1 THC 100
2 CBD 100
Drug.history 1 No drug history 100
2 Past drug history 100
Tests of Between-Subjects Effects
Dependent Variable: short.term.memory
Source Type III Sum of Squares df Mean Square F Sig.
Corrected Model 92.600a 3 30.867 5.586 .001
Intercept 2506.320 1 2506.320 453.557 .000
Marijuana.dosage 12.500 1 12.500 2.262 .134
Drug.history .720 1 .720 .130 .719
Marijuana.dosage * Drug.history 79.380 1 79.380 14.365 .000
Error 1083.080 196 5.526
Total 3682.000 200
Corrected Total 1175.680 199
a. R Squared = .079 (Adjusted R Squared = .065)

GRAPH
/HISTOGRAM=short.term.memory.

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