EPI 202 Lab 1
1.
In a study of malnutrition and diarrhea in children under age five in
Sudanese community, 154 episodes of diarrhea were observed in
38.51 personyears of observing among children who were 75% or
less the expected weight for their age, and 287 episodes of
diarrhea were observed in 88.83 personyears of observation
among children who were 90% or more of the expected weight for
their age (EI Samani et al; Am J Epidemiol, 1988).
a.
Construct an appropriate table to describe the data, and calculate
the incidence rates for each of the two groups.
< 75%
> 90%
Case
154
287
441
Person Years
38.51
88.83
127.34
IR (PYs)
4.00
3.23
b. Test the hypothesis that there is no association between
malnutrition and rate of diarrhea. Interpret the numeric results
succinctly.
H
0
: There is no association between diarrhea and expected weight
less than 75%.
(I
1
=I
0
I
1
I
0
= 0 I
1
/I
0
= 1 ln(I
1
/I
0
) = 0)
HA: There is association between diarrhea and expected weight less
than 75%. (I
1
≠I
0
I
1
I
0
≠0 I
1
/I
0
≠1 ln(I
1
/I
0
)≠0)
Z
2
=
[
X
−
E
(
X

H
0
)
]
2
Var
(
X

H
0
)
x
1
2
X
=
154
T
=
¿
133.36
E
(
X

H
0
)
=
M
1
×N
1
/
¿
^
Var
(
X

H
0
)
=
M
1
N
1
N
0
T
2
=
93.04
Z
2
=
[
X
−
E
(
X

H
0
)
]
2
Var
(
X

H
0
)
=
426.0
93.04
=
4.57
Pr
[
x
2
>
4.57
]
=
0.04
<
0.05
We reject the null hypothesis at the 0.05 level of significance.
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 Summer '14
 FrancisCook