help sheet for spss prntouts

5/25/2018 Help Sheet for Spss Prntouts

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SPSS Help 1

Help Sheet for Reading SPSS PrintoutsHeather Walen-Frederick, Ph.D.

This document will give ou annotated SPSS output !or the !ollowing statistics"

1. #orrelation$. %egression&. Paired Samples t-test'. (ndependent Samples t-test). *+*. #hi S/uare

+ote that the version o! SPSSused !or this handout was 13.00asic2. There!ore, i! ou have advancedadd-ons, or a more recent version there ma 3e some slight di!!erences, 3ut the 3ulk should 3e the same.ne possi3le di!!erence would 3e !or later versions or advanced packages to give the option o! things likee!!ect si4e, etc. (n addition, the data used !or these printouts were 3ased on data availa3le in the te5t"Statistics for the Behavioral Sciences, 4thEdition (Jaccard & Becker, 00!.

This guide is meant to 3e a help6 it should not replace reading the te5t, our class notes, the *P* manualor simpl using our head. (! ou have trou3le with data entr, or other items not addressed in this guide,please tr using the SPSS help that comes with the program 0when in SPSS, go under the 7help8 ta3 andclick on 7topics86 ou ma 3e surprised at how 7user !riendl8 SPSS help reall is2. *t the end o! thisdocument is a guide to assist ou in picking the most appropriate statistical test !or our data.

Note:+o test should 3e conducted without F(%ST doing e5plorator data analsis and con!irming that thestatistical analsis would ield valid results. That is, check that the assumptions !or each test are met, orthat the test is ro3ust against violation0s2. Please do thorough e5plorator data analsis, to check !oroutliers, missing data, coding errors, etc. %emem3er" 9ar3age in, gar3age out:

" note a#out statistical significance ($hat it %eansdoes not %ean!.

;ost everone appreciates a 7re!resher8 on this topic.

Statistical Significance'*n o3served e!!ect that is large enough we do not think we got it on accident0that is, we do not think that the result we got was due to chancealone2.

Ho$ do $e decide if so%ething is statisticall significant)(! H< is true, thep-value 0pro3a3ilit value2 is the pro3a3ilit that the o3served outcome 0or a value moree5treme than what we o3serve2 would happen. Thep-value is a value we o3tain a!ter calculating a teststatistic. The smaller thep-value, the stronger the evidence againstthe H


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SPSS Help $

Because these are lo$ pro#a#ilities (eents not likel to happen if the null were true!, $e reect thenull $hen our calculatedp+alue falls #elo$ these alpha leels.

4hat if ourp+alue is close to alpha, #ut slightl oer it (like .056!) Cou cannot reect the null.However, ou can state that it is 7marginall8 signi!icant. Cou will want to look at our e!!ect si4e todetermine the strength o! the relationship and also our sample si4e. !ten, a moderate to large e!!ect will

not 3e statisticall signi!icant i! the sample si4e is low 0low power2. (n this case, it suggests !urtherresearch with a larger sample.

Please remem3er that statistical signi!icance does not e/ual importance. Cou will alwas want tocalculate a measure o! e!!ect si4e to determine the strength o! the relationship. *nother thing to keep inmind is that the e!!ect si4e, and how important it is, is somewhat su3ective and can var depending onthe stud at hand.

1. orrelation

* correlation tells ou how and to what e5tent two varia3les are linearl related. Ese this techni/ue whenou have two varia3les 0measured on the same person2 that are /uantitative in nature and measured on alevel that at least appro5imates interval characteristics. When conducting a correlation, 3e sure to look at

our data, including scatterplots, to make sure assumptions are met 0!or correlation, outliers can 3e aconcern2.

This e5ample is !rom #hapter 1' 0pro3lem 'G2. The /uestion was whether there was a relationship3etween the amount o! time it took to complete a test and the test score. Do people who take longer get3etter scores, ma3e due to re-checking /uestions and taking their time 0positive correlation2, or dopeople who !inish sooner do 3etter possi3l 3ecause the are more prepared 0negative correlation2@

This is the de!ault output.

This 3o5 gives the results.

.orrelations

1 .


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SPSS Help &

. Regression

* regression is tpicall used to predict a D with an ( 0or multiple (s2. (t is a procedure that is closelrelated to correlation 0as such, look at our data 3e!ore per!orming a regression, paing particularattention to outliers2.

This regression is 3ased on pro3lem )


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SPSS Help '

A write up would loo- li-e A regression analysis, predicting GPA scores from GRE scores, wasstatistically significant, F(2,3 4 21#56,p7 #1% (or F(2,3 4 21#56,p4 #12'# /ou would want to report yourR', explain it and if the analysis was performed to be used for actual prediction, you would want to addthe regression e"uation (see below and something li-e 0or e!ery one unit increase in GRE score, thereis a corresponding increase in GPA of #11%#

This box gi!es you the coefficients related to a regression#.oefficientsa

.'11 .G


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SPSS Help )

p-value2. This is 3elow 0less than2 an alpha o! .0&.$$O '2 A .IIQ. Thismeans IIB o! the varia3ilit in the D 0test scores2 is due to the ( 0condition26 this is a large e!!ect: Coucould also report the G)B con!idence interval 0.GG R I.'12. This interval is giving ou a range o! test scoredi!!erences6 we know there is a di!!erence in the test scores 3ased on condition. How 3ig is the di!!erence3etween the mean scores@ ur 3est guess is somewhere 3etween a3out 1 point 0.GG2 and I points0I.'12.

:. *ndependent Sa%ples t+test

*n independent samples t-test is like a paired samples t-test, in that there are two meansto compare. (t isdi!!erent in that the means are not related 0!or e5ample, means !rom a treatment and control group2. Donot !orget to check that assumptions !or a valid test are met 3e!ore per!orming this analsis.

This e5ample is 3ased on pro3lem )I in #hapter 1


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SPSS Help

;roup Statistics

1' 1.I)I 1.&$''G '.&$G

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