30 PRINT " The Poisson distribution is a one-tailed exact test that applies specifically ":PRINT " when the number of SUCCESSES can be counted but the number of FAILURES cannot."
35 PRINT TAB(8);"It can also be used to approximate the binomial distribution":PRINT TAB(4);"when the number of trials is > 100 and the the population rate is < 5% ."
40 LOCATE 11,22:PRINT "Enter the number of cases OBSERVED:"
45 AR=11:AC=60:GOSUB 4800:I=VAL(IP$):IF INT(I)=I THEN XO=I ELSE BEEP:LOCATE 25,21:PRINT "Observed number must be an integer.";:GOTO 45
50 LOCATE 13,22:PRINT "Enter the number of cases EXPECTED:"
55 PRINT TAB(29);"(may be a fraction)":PRINT TAB(20);"(e.g. population rate * time interval)":AR=13:AC=60:GOSUB 4800:E=VAL(IP$)
60 COLOR 23:LOCATE 17,28:PRINT "CALCULATING PROBABILITY"
65 AF=0:YO=XO:CE=0:IF E<YO THEN YO=YO-1:AF=1
70 IF YO=0 THEN SF=1 ELSE SF=E+1
75 F=E:FOR Z=2 TO YO:F=F*E/Z:IF F>1E+22 THEN F=F*0:SF=SF* 0:CE=CE+1
80 IF F>=0 THEN SF=SF+F:NEXT Z
85 SL=LOG(SF)-E+CE*50:IF SL>80 THEN P=0 ELSE P=EXP(SL)
90 IF AF=1 THEN P=1-P
95 PLAY "MS O3 L64 G O2 GE L9 E"
100 COLOR CLR2,CLR1:LOCATE 17,1:PRINT TAB(8);"The probability of observing ";XO;" or ";
105 IF AF=1 THEN PRINT "more cases "; ELSE PRINT "fewer cases ";
110 IF P<9.99E-07 THEN PRINT "< 10 (-6)"; ELSE IF P>0.95 THEN PRINT "> .95"; ELSE PRINT "= ";P;
115 PRINT TAB(80):COLOR CLR1,CLR2:LOCATE 25,6:INPUT;"Do you want to perform another Poisson distribution calculation? ",A$:IF A$="y" OR A$="Y" THEN 20
120 GOTO 3000
5000 BEEP:IF ERR<>53 AND ERR<>71 THEN 5010 ELSE LOCATE 2,10:PRINT "Please place EPISTAT in drive A: (or other default).":PRINT TAB(25);"Press any key to continue:"
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