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Sampling With Replacement

Sampling With Replacement. How the program works a54p10.sas. The Simulation part of SRSWR N=3, n=2. %LET total=6; *Total number of elements in population; %LET tsamp=3; *Total number of elements in the sample;

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Sampling With Replacement

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  1. Sampling With Replacement How the program works a54p10.sas

  2. The Simulation part of SRSWRN=3, n=2 • %LET total=6; *Total number of elements in population; • %LET tsamp=3; *Total number of elements in the sample; • %LET nsamp=40; *Number of samples to Select ; DATA d (KEEP=sample sid1-sid3 s1-s3 ); SET pop1; ARRAY x{&total} ; *Original values; ARRAY id{&total}; *Original ids; ARRAY s{&tsamp}; *Sample; ARRAY sid{&tsamp}; DO sample=1 to &nsamp; DO j=1 TO &tsamp; *Randomly select permutations; rn=INT(&total*RANUNI(54231))+1; s{j}=x{rn}; sid{j}=rn; END; OUTPUT; END; RUN;

  3. The Simulation part of SRSWRN=3, n=2 (without macro vars) DATA d (KEEP=sample sid1-sid3 s1-s3 ); SET pop1; ARRAY x{6} ; *Original values of response; ARRAY id{6}; *Original subject ids; ARRAY s{2}; *Sample values; ARRAY sid{2}; *Sample subject ids; DO sample=1 to 40; * Number of samples to select; DO j=1 TO 2; * Randomly select a subject; rn=INT(6*RANUNI(54231))+1; s{j}=x{rn}; sid{j}=rn; END; OUTPUT; END; RUN;

  4. Uniform random number generator • RANUNI(54231) • A function in SAS • It picks at random a number between 0 and 1 • Example: x=RANUNI(3242); • x=0.321234 • Problem: Write a SAS program to generate 10 uniform random numbers between 0 and 1, and list the numbers.

  5. Uniform random number generator Example: x=RANUNI(3242); x=0.321234 Goal: To randomly select a subject in a population of N=6 subjects. Strategy: Multiply random number by (N): x1=6*RANUNI (3242); Example: x1=1.9274 The random number now ranges from 0 to 6. Take the integer part: x2=INT(6*RANUNI(3242)); Example: x2=1 Add 1 to make it go from 1 to N: x3=INT(6*RANUNI(3242))+1; Example: x3=2;

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