Chapter 6: Study Designs: Ecologic, Cross Sectional, Case Control

Question 1

Ecologic comparison studies?

Answer 1

sometimes called cross sectional ecologic studies. an assessment of the correlation between exposure rates and disease rates among different groups or pop. over the same time period

Question 2

Ecologic trend?

Answer 2

also called time series. examination of correlation of changes in exposure w/ changes in disease over time w/in the same community, country, etc.

Question 3

Ecologic fallacy?

Answer 3

an erroneous inference that may occur b/c an association observed between variables on an aggregate level does not necessarily represent or reflect what actually exists

Question 4

Cross-sectional study?

Answer 4

also called a prevalence study. exposure and disease measures are obtained at the level of the individual.
-a type of observational study that analyzes data from a pop. or a representative subset, at a point in time
Ex: studying development psych. taking people of different ages and investing their behaviors all at once
Ex: prevalence of tobacco consumption (pg. 666)

Question 5

What are the types of cross sectional studies?

Answer 5

• Probability samples

- Non probability samples

Question 6

What are types of probability samples?

Answer 6

every element has in the pop. has a nonzero probability of being included in the sample

• Simple random sample
• Systemic sample
• Stratified sample

Question 7

What are types of non probability samples?

Answer 7

based on a sampling plan w/o that feature

• Quota sample
• Judgmental sample

Question 8

Simple random samples?

Answer 8

a type of sample where each person in the pop. has an equal probability of being selected. Requires all potential subjects to be counted before sampling

Question 9

Systematic sample?

Answer 9

the procedure of selecting according to some systematic rule. like all people’s name begin w/ the same letter or they’re born on the same day, etc.

Question 10

Sampling unit?

Answer 10

that element or set of elements considered for selection in some stage of sampling. In epidemiologic research, it’s usually a specific person picked

Question 11

Stratified sampling approach?

Answer 11

the pop. is divided into mutually exclusive and exhaustive strata; sampling is performed in each stratum or distinct subgroup

Question 12

Case control study?

Answer 12

a type of analytic study of people w/ a disease of interest and those w/o the disease as a comparison group.

Question 13

What is matching?

Answer 13

the process of making cases and controls equivalent w/ respect to factors other than the exposure or factor that is being investigated

Question 14

Individual matching?

Answer 14

the use of matched pairs

Ex: to match each case w/ 1 or more controls who are the same age/gender

Question 15

Frequency matching?

Answer 15

group matching. equal distributions of demographic variables like age/gender are maintained among the cases and controls

Question 16

What is overmatching?

Answer 16

the case and controls are too closely matched or matched on too many variables. this can obscure casual associations between exposures and disease outcomes and should be avoided

Question 17

Odds ratio?

Answer 17

the ratio of 2 odds. a statistic that quantifies the strength of the association between 2 events A and B
-(A/C) / (B/D) or (A/D) /(B/C)
- yes yes/no no / yes no no yes
-To interpret, subtract 1 from the OR and multiply by 100
-Ex: (139953)/(55058)=4.15;
Interpret?: 4.15-1*100=315%

Question 18

concordant pairs?

Answer 18

both members of the pair have either been exposed or or not exposed to the study

Question 19

discordant pairs?

Answer 19

a situation which 1 member of a pair has been exposed and the other was not
Ex: Figure 6-21 (pg. 711)

Question 20

What is in an experimental research/study design?

Answer 20

used to test the effect of new treatments, tools, and programs to see if they prevent or cure disease

• manipulate study factors
• randomizes study subjects
• Ex: field trials, randomized control trials (RCTs), and community interventions

Question 21

What is a quasi experimental research?

Answer 21

used to asses real world effectiveness

-manipulates study factor w/o randomization of study subjects

Question 22

What is observational research?

Answer 22

used to watch the natural exposure-disease relationship

• no manipulation of study factors nor randomization of study subjects
• Ex: case controls, ecologic, case report, cohort study, etc.

Question 23

What are ecological studies?

Answer 23

meant to understand the relationship between outcome and exposure at a pop. level

Question 24

In ______ studies, the investigator introduces or withholds an exposure in order to determine its effects and randomizes participants. In _____ studies, subjects are studied under natural circumstances; participants are not assigned to exposure.

Answer 24

Experimental, observational

Question 25

Select all the factors which help epidemiologists to determine the most appropriate study design for evaluation a particular association.

Answer 25

• The hypothesis being tested
• The state of knowledge on the topic
• Ethics and feasibility

Question 26

2x2 table?

Answer 26

Used to find odds ratio, relative risk, etc.

• Disease always on top and exposure is on the side
• look at sample questions