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Unformatted text preview: ions for paired
data.
Example: Two chemotherapy regimens for breast cancer after
mastectomy are to be compared. A matched study is set up
such that patients are assigned to pairs matched on age
(within 5 years) and clinical conditions. A random member of
each matched pair gets treatment A (chemotherapy)
perioperatively (within 1 week after mastectomy) and for an
additional six months, whereas the other member gets
treatment B chemotherapy only perioperatively. The patients
are followed for 5 years with survival as the outcome variable.
The rate of 5 year survivals were 526/621 and 515/621 for
treatments A and B, respectively.
Chapter 10: Hypothesis Testing: Categorical Data Stat 491: Biostatistics Introduction
TwoSample Test for Binomial Proportions
McNemar’s Test
Estimation of Sample Size and Power
R × C Contingency Tables
ChiSquare GoodnessofFit Test
The Kappa Statistic McNemar’s Test: Introduction Cont’d...
Assuming independent samples (WRONG assumption),
prop.test(x=c(526,515),n=c(621,621))
gives a pvalue= 0.441 which implies no signiﬁcant diﬀerence
between the two treatments.
A more appropriate analysis of the data is using matched pairs
as sampling units.
Outcome for
Treatment B
Outcome for Treatment A survive Die Total
Survive
510
16
526
Die
5
90
95
Total
515
106 621
Chapter 10: Hypothesis Testing: Categorical Data Stat 491: Biostatistics Introduction
TwoSample Test for Binomial Proportions
McNemar’s Test
Estimation of Sample Size and Power
R × C Contingency Tables
ChiSquare GoodnessofFit Test
The Kappa Statistic McNemar’s Test: Concordant and Discordant Pairs
A concordant pair (discordant pair) is a matched pair in which
the outcome is the same (diﬀerent) for each member of the
pair.
A type A discordant pair is a matched pair in which the
treatment A member of the pair has the event but treatment
B member does not.
A type B discordant pair is a matched pair in which the
treatment B member of the pair has the event but treatment
A member does not.
The concordant pairs provide no information about diﬀerenc...
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 Fall '12
 SolomonHarrar
 Statistics, Biostatistics

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