Introductory Biostatistics

leading to

^pp¼

x

n

ðsample proportionÞ

2. For the Poisson distribution,

Lðx;yÞ¼

Yn

i¼ 1

yxie
y

xi!

leading to

yy^¼

P

xi

n

¼x ðsample meanÞ

3. For the normal distribution,

Lðx;m;yÞ¼

Yn

i¼ 1

1

s

ffiffiffiffiffiffi

2 p

p exp

ðxi
mÞ^2

2 s^2

"

leading to

mm^¼x

Matched Case–Control Studies Pair-matched case–control studies with a
binary risk factor were introduced near the end of Chapter 3. To control con-
founding factors in this design, individual diseased cases are matched one to
one to a set of controls, or disease-free persons, chosen to have similar values
for important confounding variables. The data are represented by a 22 table
(Table 4.12) whereðþ;
Þdenotes (exposed, unexposed) categories. Letybe
the odds ratio associated with the exposure under investigation;n 10 was shown
to have the binomial distributionBðn;pÞ, where

TABLE 4.12

Case

Control þ


þ n 11 n 01


 n 10 n 00

172 ESTIMATION OF PARAMETERS