Study Guide

Question 1

Odds Ratio? (formula)
Self-reported cross-sectional data obtained via questionnaire between 1993 and 1997 from 31,173 wives were used. Wives were asked about current and past use of specific pesticides and groups of pesticides based on function (fungicides, herbicides, insecticides, and fumigants).
Among 31,173 wives surveyed, 8.2% of 281 women with retinal degeneration and 4.7 % of those without retinal degeneration reported ever use of fungicides.

Create a table, fill it in, and find the odds ratio?

Answer 1

A. 23
B. 1452
C. 258
D. 29440
Total of those w/ fungicide: 1475
Total of those w/o fungicide: 29698
Total: 31,173
Total of those w/ RD: 281
Total of those w/o RD: 30892
Odds ratio: (a*d)/(b*c)= (23*29440)/(1452*258)= 1.8
Interpret?: 1.8-1*100= 80%

Question 2

Relative Risk? (RR)
In a study of radiation exposure and breast cancer, 500 participants with breast cancer and 1000
participants without breast cancer are compared. It is learned that 400 of the participants with breast
cancer and 600 of the participants without breast cancer were exposed to radiation for prolonged
period of time at some point in their life, prior to diagnosis. We later learned from a government report
that the incidence of breast cancer in the total population is 30% and the prevalence to radiation
exposure is 50% .
Create a 2 x 2 table.

Answer 2

a/(a+b) / c/(c+d)

Question 3

Attributable Risk?

Answer 3

a/(a+b) - c/(c+d)

Question 4

Attributable Fraction? (AF)

Answer 4

RR-1 /RR

Question 5

Pop. Attributable Fraction? (PAF)

Answer 5

The proportion of cases for an outcome that can be attributed to a certain risk factor for the whole pop.
P(R-1) / P(R-1)+1

Question 6

Sensitivity?

Answer 6

true positive rate. the proportion of samples that are genuinely positive and give a positive result
Ex: a test that identifies all positive samples in a panel is very sensitive
a/a+c (vertical)

Question 7

Specificity?

Answer 7

true negative rate. the proportion of samples that test negative
-Ex: a test that identifies all healthy people as negative for a specific illness
d/b+d

Question 8

Positive Predictive Value? (PPV)

Answer 8

a/a+b

Question 9

Negative Predictive Value? (NPV)

Answer 9

d/c+d

Question 10

Cause specific death rate?

Answer 10

(# of deaths from a specified cause/total pop.)* 100,000

Question 11

Case fatality Ratio?

Answer 11

(# of cases who died/total # of cases)* 100

Question 12

Disadvantages of this study design include the following: should not be used to study disease etiology and exposure-disease temporality not ascertained

Answer 12

Cross sectional study

Question 13

Which study design’s unit of observation is a group and uses existing study data?

Answer 13

Ecologic study

Question 14

This study design cannot directly measure risk and instead uses the odds ratio

Answer 14

Case control

Question 15

The main type of bias with this study design is selection bias

Answer 15

Cohort

Question 16

This study design is useful for studying rare diseases

Answer 16

Case control

Question 17

This is a quick and inexpensive study design and often uses data from surveys

Answer 17

Cross sectional

Question 18

In this type of study, participants are given a new medication but not randomized

Answer 18

Intervention or Quasi Experimental

Question 19

In this study, a team of investigators gathered data on a group of individuals who were exposed to secondhand smoke about 10 years ago. Then the team determines if any developed different types of cancers.

Answer 19

Retrospective cohort

Question 20

Insulin to prevent the complications of diabetes. What kind of prevention?

Answer 20

Tertiary

Question 21

Healthy eating to prevent diabetes. Prevention?

Answer 21

Primary

Question 22

Blood glucose testing to detect diabetes. Prevention?

Answer 22

Secondary

Question 23

True or false: Specificity is affected by the prevalence of a given disease

Answer 23

False; PPV and NPV are influenced by prevalence of a disease