L.4.1.1 WATTOX.SAS program statements (Cont.)

/* Delete data not needed for the dilution water-100 percent

elutriate comparison. */

/* Print descriptive statistics. */

DATA A;

SET A0;

IF TRT>1 THEN DELETE;

TITLE2 'ARCSINE-SQUARE ROOT TRANSFORMATION';

PROC MEANS NOPRINT; VAR ARCSURV; BY TRT; ID M;

OUTPUT OUT=X N=N MEAN=MEAN VAR=VARIANCE STD=S STDERR=SE;

PROC PRINT LABEL; VAR TRT N MEAN VARIANCE S SE;

/* Test normality of residuals using Shapiro-Wilk's Test. */

PROC GLM DATA=A NOPRINT;

CLASS TRT;

MODEL ARCSURV=TRT;

OUTPUT OUT=Z R=RESID;

PROC UNIVARIATE NORMAL DATA=Z;

VAR RESID;

TITLE3 'SHAPIRO-WILKS TEST';

/* Conduct t-test, which includes F? test for equality of

variances. */

PROC TTEST DATA=A;

CLASS TRT;

VAR ARCSURV;

/* Convert data to rankits and conduct t-test. */

PROC RANK DATA=A NORMAL=BLOM OUT=A1;

VAR SURV; RANKS RANKIT;

PROC TTEST DATA=A1;

CLASS TRT;

VAR RANKIT;

TITLE2 'DATA CONVERTED TO RANKITS';

/* Calculate minimum significant difference and power of a

t-test to detect */

/* true population differences of 10, 20, 30, 40 and 50

percent below mean */

/* dilution water survival. */

DATA B0;

MERGE X Y;

IF TRT=0;

MEAN0=MEAN; N0=N; S20=VARIANCE;

MEANPCT=MEANSURV/M;

DATA B1;

SET X;

IF TRT=1;

N1=N; S21=VARIANCE;

DATA B2;

MERGE B0 B1;

DF=N0+N1-2;

N=(N0+N1)/2;

S2POOL=(S20*(N0-1)+S21*(N1-1))/DF;

TALPHA=TINV(.95,DF);

DMIN=TALPHA*SQRT(2*S2POOL/N);

L42

Appendix L Selected Resource Documents