Sample Size

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2SampleSizeThe rstquestionfacedbya statisticalconsultant,andfrequentlythela st,is, Howmany subjects(animals,units)doI need? , TypeII error, andone sidedversustwo questionistosettlethetypeofvariable(endp oint)theconsulteehasinmind:Isit continuous,discrete,orsomethingelse?Forc ontinuousmeasurementsthenormaldistributi onisthedefaultmodel,fordistributionswith binaryoutcomes, samplesizecalculation,foroneortwo groups,are:TypeI Error( )Probabilityofrejectingthenullhypothesis whenit is trueTypeII Error( )Probabilityofnotrejectingthenullhypothe siswhenit is falsePower=1 Probabilityofrejectingthenullhypothesisw henit is false 20and 21Variancesunderthenullandalternative hypothe ses(maybethesame) 0and 1Meansunderthenullandalternative hypothesesn0andn1Samplesizesintwo groups(maybethesame)T

BEGIN WITH A BASIC FORMULA FOR SAMPLE SIZEŒLEHR’S EQUATION 29 right (equivalent to increasing the distance between null and alternative hypotheses)

  Samples, Size, Sample size