Test for Mean Difference (Final)

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


Pre-Test and the Post-test Performance.


There is a significant difference between the Pre-

Test and the Post-test Performance.


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Null Hypothesis


variance of the Pre-Test and the Post-testPerformance.


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:

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Test for Mean Difference (Final)