## Calculating a t-test in SPSS in order to compare differences between means and/or proportions

**What you’ll need variable-wise: **

For comparing mean differences between groups: a dichotomous (binary) independent variable and an interval-ratio dependent variable.

For comparing differences in proportions between groups: a dichotomous (binary) independent variable and a dummied dependent variable (i.e. a variable coded 1/0).

**The steps in SPSS for calculating a t-test for comparing two independent means or proportions**.

- Analyze –> compare means –> Independent Sample t-tests
- move your dependent variable (the interval variable for testing means or dummy for testing differences in proportions) into the Test Variables box
- move the independent (dichotomous) variable into the grouping variable box à click on define groups –> type in what the categories of the dichotomous variable are (1 & 0 or 1 & 2 or whatever they are)
- Click on options and make sure to tick “exclude cases listwise” (you can also change the confidence level from 95% to something else
- Click OK (or paste if you want to use syntax)

**Your Output will look like this: **

**How these data should be presented in a table in a paper:**

**To do the same thing using syntax: **

*check your work with a crosstab*.

crosstabs marstat by dummarcom.

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* Recoding your variables *

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*create a binary independent variable*.

RECODE MARSTAT (1=1) (2=1) (SYSMIS=SYSMIS) (3 thru 6=0) (ELSE=SYSMIS) INTO DumMarCom.

VARIABLE LABELS DumMarCom ‘Dummy for Married/CommonLaw’.

recode CHINHSDC (1 thru 3=1) (0=0) (else=sysmis) (sysmis=sysmis) into dumHasKidsHousehold.

variable labels dumHasKidsHousehold ‘Dummy for Has Kids’.

*check your work with a crosstab*.

crosstabs CHINHSDC by dumHasKidsHousehold .

*explore the interval-ratio variable with a frequency table or descriptive statistics to make sure that missing data is not included in the analyses*.

freq hsdsizec.

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* Running t-Tests *

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T-TEST GROUPS=DumMarCom(1 0)/MISSING=LISTWISE/VARIABLES=dumHasKidsHousehold HSDSIZEC /CRITERIA=CI(.95).

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