1 epidemiologic studies that are concerned with characterizing the amount and distribution of health...
TRANSCRIPT
1
Epidemiologic studies that are concerned with characterizing the amount and distribution of
health and disease within a population.
Descriptive Epidemiology
Teach Epidemiology
Making Group Comparisons and Identifying Associations
2
Epidemiologic studies that are concerned with determinants of disease and the reasons for relatively high or low frequencies of
disease in specific population subgroups.
Analytical Epidemiology
Teach Epidemiology
Making Group Comparisons and Identifying Associations
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Hypothesis
Formulating
Descriptive Epidemiology
Testing
Analytical Epidemiology
An unproven idea, based on observation or reasoning, that can
be supported or refuted through investigation
An educated guess
Making Group Comparisons and Identifying Associations
Teach Epidemiology
4
Hypothesis:
Buprenorphine will stop heroin addicts from using heroin.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
5
PopulationTrial 1
Making Group Comparisons and Identifying Associations
6
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
Trial 1
Making Group Comparisons and Identifying Associations
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Population
150 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
21 Heroin Addicts Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
8
Bupe
Tested Positive for Heroin Total
10021 79
Tested Negative for Heroin
Trial 1
Teach Epidemiology
Making Group Comparisons and Identifying Associations
9
When you can measure what you are speaking about,
and express it in numbers, you know something about it.
Lord Kelvin
But when you cannot measure it, when you cannot express it in
numbers, your knowledge is of a meager and unsatisfactory kind.
Teach Epidemiology
Making Group Comparisons and Identifying Associations
10
A measure of how often an outcome occurs in a defined population in a defined period of time. It consists of a numerator and a denominator.
Risk
The numerator is the number of people in the population or sample who experienced the outcome and the denominator is the total number of people in the population or sample.
Population / Sample
Outcome
Denominator
Numerator
Teach Epidemiology
Making Group Comparisons and Identifying Associations
11
… the risk of a positive heroin tests is 79 / 100 per 10-week period
79 tested positive for heroin
100 study subjects
Numerator
Denominator
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Risk
12
A measure of how often an outcome occurs in a defined group of people
in a defined period of time.
The likelihood of an outcome occurring.
Risk / Rate
Teach Epidemiology
Making Group Comparisons and Identifying Associations
13
Trial 1
Bupe
Tested Positive for Heroin
10021 79
Tested Negative for Heroin
21
100or 21 %
Calculating Risk
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Risk of
Negative Heroin
Test
Total
14
Process of predicting from what is observed in a sample to what is true for the entire population.
Inference
Teach Epidemiology
Making Group Comparisons and Identifying Associations
15
Trial 1
What does this tell you about the hypothesis?
Buprenorphine will stop heroin addicts from using heroin.
InferenceProbe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Bupe
Tested Positive for Heroin
10021 79
Tested Negative for Heroin
21
100or 21 %
Risk of
Negative Heroin
Test
Total
16
People who participate in a trial, but do not get the treatment.
People whose results are compared to the group that was treated.
Control Group
Teach Epidemiology
Making Group Comparisons and Identifying Associations
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21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Control Group
Extend and label the table to include a control group.
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Risk of
Negative Heroin
Test
Total
18
100?
100or ? %No Bupe
Control Group
Making Group Comparisons
Teach Epidemiology
Making Group Comparisons and Identifying Associations
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Risk of
Negative Heroin
Test
Total
19
100?
100or ? %No Bupe
Making Group Comparisons
Teach Epidemiology
Making Group Comparisons and Identifying Associations
21
100or 21 %1007921
Tested Positive for Heroin
Tested Negative for Heroin
Bupe
Exposure
Outcome / Disease
a b
c d
Risk of
Negative Heroin
Test
Total
20
21
100or 21 %
Total
1007921Bupe
100?
100or ? %No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
A cross-classification of data where categories of one variable
are presented in rows and categories of another variable
are presented in columns
The simplest contingency table is the 2x2 table.
Contingency Table
Teach Epidemiology
Making Group Comparisons and Identifying Associations
22
Population
500 Heroin Addicts
Sample 100
Heroin Addicts
10 Weeks
21 Heroin Addicts Tested Negative for Heroin
Trial 1
Making Group Comparisons and Identifying Associations
23
Trial 2
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
?
100? %
a b
c d
Bupe
Tested Negative for Heroin
Tested Positive for
Heroin
No Bupe 100
100?
100? %
Risk of
Negative Heroin
Test
24
E
Assigned
E
O
O
O
OHeroin AddictsVolunteer Heroin Addicts
Teach Epidemiology
Making Group Comparisons and Identifying Associations
25
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Probe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
26
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
27
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
28
When you can measure what you are speaking about, and express it in numbers, you know something about it.
Lord Kelvin
But when you cannot measure it, when you cannot express it in
numbers, your knowledge is of a meager and unsatisfactory kind.
Teach Epidemiology
Making Group Comparisons and Identifying Associations
29
The value obtained by dividing one quantity by another
Ratio
Teach Epidemiology
Making Group Comparisons and Identifying Associations
30
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Ratio: The value obtained by dividing one quantity by another
Risk Ratio: The ratio of two risks
1
Risk Ratio
31
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
Ratio: The value obtained by dividing one quantity by another
Risk Ratio: The ratio of two risks
1
Risk Ratio
Create a formula
a
a + b
c
c + d
32
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
1
Risk Ratio
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
Relative Risk
33
21
10021%21 79 100 or
a b
c d
Bupe
Trial 2
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
21
10021%21 79 100 or
1
Risk RatioRelative Risk
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
The inference here is that there is no effect of Buprenorphine
34
Trial 3
Teach Epidemiology
Making Group Comparisons and Identifying Associations
?
100? %100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
?
100? %100 or
35
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Trial 3
36
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Trial 3
37
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population
Trial 3
38
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
0.34
Trial 3
39
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
0.34
The heroin addicts who received Bupe were ___ times as likely to use heroin as those who did not receive Bupe.
0.34
Trial 3
40
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
62
10062%62 38 100 or
Relative Risk
0.34
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population.
Trial 3
41
Trial 4
Teach Epidemiology
Making Group Comparisons and Identifying Associations
?
100? %100 or
a b
c d
Bupe
No Bupe
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
?
100? %100 or
42
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
Trial 4
43
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Trial 4
44
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
Relative Risk: The ratio of the risk of an outcome among the exposed to the risk of the outcome among the unexposed.
3.5
Trial 4
45
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
3.5
The heroin addicts who received Bupe were ___ times as likely to use heroin as those who did not receive Bupe.
3.5
Trial 4
46
21
10021%21 79 100 or
a b
c d
Bupe
No Bupe
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
6
1006%6 94 100 or
Relative Risk
3.5
Inference: Process of predicting from what is observed in a sample
to what is occurring in the entire population.
Trial 4
47
21
10021%21 79 100 orBupe
Trial 1
Teach Epidemiology
Making Group Comparisons and Identifying Associations
Total
Tested Negative for Heroin
Tested Positive for Heroin
Risk of
Negative Heroin
Test
What do the results tell us about the hypothesis that Buprenorphine will stop heroin addicts from using heroin?
Nothing
48
Trial 1 Trial 2
Trial 3 Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
49
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
100
50
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
100
51
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
52
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
1
Bupe is not associated with having a negative tests for heroin.
53
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative tests for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
54
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative tests for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
1006 9490
or 6%6
100
Bupe is associated with having a negative test for heroin.
3.5
55
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative tests for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
1006 9490
or 6%6
100
Bupe is associated with having a negative test for heroin.
3.5
Nothing
Compared to what?
56
6.
Buprenorphine
Buprenorphine & Naloxone
Placebo
Handout
Teach Epidemiology
Making Group Comparisons and Identifying Associations