Kruskal-SPSS

7/23/2019 Kruskal-SPSS

http://slidepdf.com/reader/full/kruskal-spss 1/6

Kruskal-Wallis ANOVA with SPSS

Dr. Hussam El-Gayar of the Urology & Nephrology Center at MansouraUniversity in Egypt found my SSS lessons and as!ed me a "uestion a#out the

analysis of some of his data. He $anted to %ompare si independent groups. His%riterion varia#le is %ontinuously distri#uted. He had already %ondu%ted a one-$ayparametri% 'N()' $ith pair$ise %omparisons. * too! a pee! at the results of thatanalysis and at the ra$ data and #e%ame %on%erned that #oth the homogeneity ofvarian%e and the normality assumptions of that analysis $ere tena#le. * split the file #ythe grouping varia#le

and o#tained the stats ne%essary to determine if the assumptions of the parametri% 'N()' $ere tena#le. Cli%! 'naly+e, Des%riptive Statisti%s. S%oot the %riterion varia#leinto the )aria#les #o. Cli%! (ptions and as! for means, varian%es, s!e$ness, and!urtosis.

Copyright /001, 2arl 3. 4uens%h - 'll rights reserved.



Descriptive Statistics

56 75.88/8 51.675 -.998 ./91 /./:/ .981

56

56 /0.157; 77.987 -./06 ./91 :.175 .981

56

56 /8.07:; 58.1:0 /.750 ./91 :;.;:1 .981

56

56 67.0905 9/;;.99; :.:/8 ./91 :.;/1 .981

56

56 .817; .989 /.8/6 ./91 :0.:51 .981

56

56 :/5.90;9 :;0;./9; .001 ./91 -:.:68 .981

56

D'<'

)alid N list$ise

D'<'

)alid N list$ise

D'<'

)alid N list$iseD'<'

)alid N list$ise

D'<'

)alid N list$ise

D'<'

)alid N list$ise

ME<H(D:.00

/.00

7.00

9.00

1.00

;.00

Statisti% Statisti% Statisti% Statisti% Std. Error Statisti% Std. Error

N Mean )arian%e S!e$ness 2urtosis

's you %an see, there is #oth great heterogeneity of varian%e and, in some #utnot all groups, great s!e$ness. *n this %ase, a nonparametri% analysis is indi%ated. 'nappropriate omni#us analysis is the 2rus!al-4allis 'N()'. <o %ondu%t it, %li%! 'naly+e,Nonparametri%s, 2 *ndependent Samples. S%oot the %riterion varia#le in the <est)aria#le 3ist and the grouping varia#le into the Grouping )aria#le #o. Cli%! Define=ange and identify the lo$est and highest numeri% values for the grouping varia#le>

/



Cli%! (2. <he output in%ludes mean ran!s for ea%h group>

Ranks

56 718.50

56 :58./5

56 /;5.6:

56 715.96

56 95.86

56 1:/.66

18/

ME<H(D:.00

/.00

7.00

9.00

1.00

;.00

<otal

D'<'N Mean =an!

Sin%e our p value is less than the .01 %riterion of statisti%al signifi%an%e, $e%on%lude that there are signifi%ant differen%es among the groups.

Test Statisticsa,b

97:.;1:

1

.000

Chi-S"uare

df

'symp. Sig.

D'<'

2rus!al 4allis <esta.

Grouping )aria#le> ME<H(D#.

4e still do not !no$ $hi%h groups differ signifi%antly from $hi%h other groups, so$e %ontinue on, %omparing ea%h group $ith ea%h other group. *f $e ma!e all possi#lepair$ise %omparisons, $e ma!e :1 %omparisons> Group : $ith /, 7, 9, 1, and ;? Group/ $ith 7, 9, 1, and ;? Group 7 $ith 9, 1, and ;? Group 9 $ith 1 and ;? and Group 1 $ith;.

7



<he Mann-4hitney U test is appropriate for %omparing t$o independent groups.Cli%! 'naly+e, Nonparametri% <ests, / *ndependent Samples. S%oot the %riterionvaria#le into the <est )aria#le 3ist and the grouping varia#le into the Grouping )aria#le#o. Cli%! Define Groups and give the group num#ers for the t$o groups to #e%ompared. Here * have as!ed to %ompare group : $ith group ;>

Cli%! (2. <he output in%ludes for ea%h group the mean ran! and sum of ran!s.@oth the Mann-4hitney and the 4il%oon =an! Sum statisti%s are given. <hese t$ostatisti%s are e"uivalent, yielding the same p value. Sin%e our p value is less than the .01 %riterion of statisti%al signifi%an%e, $e %on%lude that methods : and ; differ from ea%h

other signifi%antly.

Ranks

56 95.05 96;/.00

56 :91.5: :9:17.00

:59

ME<H(D:.00

;.00

<otal

D'<'N Mean =an! Sum of =an!s

Test Statisticsa

5.000

96;/.000

-:/.085

.000

Mann-4hitney U

4il%o&on 4

A

'symp. Sig. /-tailed

D'<'

Grouping )aria#le> ME<H(Da.

9



Having illustrated ho$ to %ompare t$o groups, * left to Dr. El-Gayar the tas! ofma!ing the remaining :9 pair$ise %omparisons.

(ne final %omment> Sin%e some of the groups are greatly s!e$ed, it is a goodidea to report medians rather than, or in addition to, means. SSS Des%riptives does

not %ompute medians, #ut SSS Bre"uen%ies does. Here is ho$ to do it> Birst, split thefile #y the grouping method. <hen %li%! 'naly+e, Des%riptive Statisti%s, Bre"uen%ies.Sele%t the %riterion varia#le and %li%! Statisti%s. Che%! Median and %li%! Continue.Cli%! Bormat and %he%! Suppress <a#les 4ith More <han Categories. Enter thenum#er / in the %ategories #o and %li%! Continue.

1



Cli%! (2. <he output in%ludes the median for ea%h group>

Statistics

D'<'

56

0

75.8800

56

0

//.0000

56

0

70.00;/

56

0

;1./100

56

0

.;609

56

0

:7:.8900

)alid

Missing

N

Median

)alid

Missing

N

Median

)alid

Missing

N

Median

)alid

Missing

N

Median

)alid

Missing

N

Median

)alid

Missing

N

Median

:.00

/.00

7.00

9.00

1.00

;.00

Copyright /001, 2arl 3. 4uens%h - 'll rights reserved.

;

Documents

Kruskal-SPSS