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7/28/2019 Test for Mean Difference (Final)
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by
Leby A. Fastidio
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T test
Independent t testDependent t test
ANOVAOne Way ANOVA
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Objectives
The independent t-test compares the means
between two unrelated groups on the samecontinuous, dependent variable. The SPSS t-test procedure allows the testing of equality ofvariances (Levene's test) and the t-value forboth equal- and unequal-variance. It alsoprovides the relevant descriptive statistics.
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Assumptions
Independent variable consists oftwo
independent groups. Dependent variable is either interval or ratio.
Dependent variable is approximately
normally distributed Similiar variances between the two groups
(homogeneity of variances).
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Null Hypothesis
There is no significant difference between the
academic performance of the male and thefemale.
Alternative Hypothesis
There is a significant difference between theacademic performance of the male and the
female.
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Click Analyze > Compare Means >Independent-Samples T Test... on the top
menu as shown below.
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A dialog box will appear:
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Put the Academic Performance" variableinto the "Test Variable(s):" box and the
Gender" variable into the "GroupingVariable:" box by highlighting the relevantvariables and pressing the buttons.
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You need to define the groups (gender). Clickthe button.
Another dialog box will appear.
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Enter 0" into the "Group 1:" box and
enter 1" into the "Group 2:" box.
Remember that we labeled the Malegroup as 0" and the Female group as
1".
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Click the button.
If you need to change the confidencelevel limits, or change how to excludecases then press the button.
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Youll be presented with this:
Then click the button. Click the button.
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You will be presented with two tables containing all the datagenerated by the Independent t-test procedure in SPSS.
Group Statistics Table - This table provides useful
descriptive statistics for the two groups that youcompared including the mean and standard
deviation.
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Independent Samples Test Table - This tableprovides the actual results from the independent
t-test and Levine's Test for Equality of Variances.
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Objectives
The dependent t-test (called the Paired-Samples T
Test in SPSS) compares the means between tworelated groups on the same continuous variable.The SPSS t-test procedure also provides relevant
descriptive statistics.
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Assumptions
Dependent variable is interval or ratio
(continuous) The differences between the two groups on the
dependent t-test approximately normally
distributed
Independent variable consists ofone group ortwo "matched-pairs" groups.
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Null Hypothesis
There is no significant difference between the
Pre-Test and the Post-test Performance.
Alternative Hypothesis
There is a significant difference between the Pre-
Test and the Post-test Performance.
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Null Hypothesis
There is no significant difference between the
variance of the Pre-Test and the Post-testPerformance.
Alternative Hypothesis
There is a significant difference between thevariance of the Pre-Test and the Post-test
Performance.
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Click Analyze > Compare Means > Paired-Samples T Test... on the top menu.
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Another dialog box will appear:
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You need to transfer the variables Pre-Test"and Post-Test" into the "Paired Variables:"
box. There are two ways to do this. You caneither highlight both variables (use the cursorand hold down the shift key and pressthe button or you can drag and drop eachvariable into the boxes) If you are using olderversions of SPSS, you will need to transferthe variables using the former method.
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Youll end up with a similar screen like this:
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If you need to change the confidence levellimits, or change how to exclude cases then
press the button. Youll be presented with this:
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Then click the button. Click the button to generate the result.
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You will be presented with 3 tables in theoutput viewer under the title "T-Test" but you
only need to look at two tables - PairedSample Statistics Table and the PairedSamples Test table
Paired Sample Statistics Table - The first table
titled Paired Sample Statistics is where SPSS hasgenerated descriptive statistics for your variables.
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The first table is shown below:
The second table titled Paired SamplesCorrelations provides you with thecorrelation between Pretest" and Posttest".
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Paired Samples Test Table - is the table where theresults of the dependent t-test are presented. As
such, the columns of the table labelled "Mean",
"Std. Deviation", "Std. Error Mean", 95% CI referto the mean difference between the two jumps
and the standard deviation, standard error and
95% CI of this difference, respectively. The last 3
columns express the results of the dependent t-test, namely the t-value, the degrees of freedom
and the significance level.
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The table is shown below: