Term
| What are 4 reasons to investigate |
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Definition
control and prevention
severity and risk to others
public, political, or legal concerns
research opportunities |
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Term
| What are the two major types of epidemiological studies? |
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Definition
observational
experimental (clinical) |
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Term
| What is an observational study? |
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Definition
investigator observes exposures and outcome without controlling either
("Natural experiment", you have no effect on exposures or outcomes) |
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Term
| What are the two types of observational studies? |
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Definition
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Term
| Describe a descriptive observational study, what questions does it answer? |
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Definition
Investigator collects information to characterize and summarize a health event
-who, what, where, and when |
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Term
| Describe an analytical observational study, what questions are answered? |
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Definition
investigator compares groups to identify risk factors
(why and how) |
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Term
| What is an experimental (clinical) study? |
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Definition
| researcher controls exposure of subjects to an intervention and observes the outcome |
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Term
| THe study factor is manipulated in what type of study, observational or experimental? |
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Definition
-in experimental you WILL manipulate some factor of the study
-in observational there is NO manipulation of the study factor |
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Term
| Randomization of study subjects needs to be present in which type of study, observational or experimental? |
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Definition
| -in experimental there needs to be randomization of the participants, w/o this there the statistical part of the data will not be valid |
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Term
| Is there both randomization and manipulation in experimental studies? |
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Definition
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Term
| Is there both randomization and manipulation in quasi-experimental studies? |
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Definition
manipulation, yes
randomization, no |
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Term
| Is there both randomization and manipulation in observational studies? |
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Definition
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Term
| What is descriptive epidemiology: what three things does it define? What does it generate? |
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Definition
-study of the occurrence and distribution of disease
-person, place, time
-HYPOTHESIS generating |
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Term
| A cross sectional study can be defined as a _________ study |
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Definition
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Term
| Cross sectional studies look at what: what do they measure? What is the period of observation? What is collected? |
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Definition
-Exposure and disease measures obtained at the individual level
-single period of observation
-exposure and disease histories collected simultaneously |
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Term
| What are three uses of cross sectional studies? |
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Definition
-hypothesis generation (you can see something happening, now you want to know "why")
-intervention planning
-estimation of the magnitude and distribution of a health problem |
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Term
| Analytical epidemiology uses ___________ groups to quantify relationships between _________ and _________ |
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Definition
comparison
exposures
outcomes |
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Term
| What does analytical epidemiology identify? |
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Definition
factors associated with disease to identify populations at risk
(by comparing groups we can come up with risk factors) |
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Term
| Analytical epidemiology includes _________ testing |
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Definition
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Term
| What are the two types of analytic studies? |
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Definition
cohort studies
case-control studies |
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Term
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Definition
| Compare groups of people who have been EXPOSED to suspected risk factors with groups who have not been exposed |
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Term
| What is a case control study? |
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Definition
| Compare people with a DISEASE (case-patients) with a group of people without the disease (controls) |
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Term
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Definition
| Group members experience a common exposure associated with a specific setting or they share a non-specific exposure associated with a general classification |
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Term
| In cohort studies, cohorts of persons placed in a group can be studies as a group two ways, what are they? |
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Definition
-forward in time (prospectively)
-backward in time (retrospectively): an ex. would be looking at stats of how well students do in the PA program and then looking at their test scores/GPAs/work experience when entering the program |
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Term
| Describe a cohort study that is purely prospective in nature |
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Definition
| characterized by determination of exposure levels at baseline (the present), and follow-up for occurrence of disease at some time in the FUTURE |
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Term
| Retrospective cohort studies make use of historical data to determine what? |
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Definition
| exposure level at some baseline in the past |
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Term
| Cohort studies involve the comparison of disease rates between what two groups? |
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Definition
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Term
| What should be the one difference between the exposed group and the non exposed group? |
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Definition
| They should be similar in demographics and geography but the non-exposed groups needs to lack exposure |
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Term
| What provides a direct measure of association between exposure and outcome? |
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Definition
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Term
| What is the relative risk? |
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Definition
| The rato of the incidence (attack rate) of disease in the exposed group to the incidence (attack rate) in the non-exposed group |
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Term
| What is the attack rate for the exposed group? |
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Definition
| It equals the number of people who were exposed and become ill (%) the total number of people exposed |
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Term
| What is the attack rate for the not exposed group? |
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Definition
| The number of people who were not exposed and became ill (%) the total number of people who were not exposed |
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Term
| HOw is relative risk computed? |
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Definition
| calculated by dividing the attack rate for people who were exposed to the item by the attack rate for those who were not exposed |
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Term
| To identify exposure of interest quickly, look for item with what three characteristics? |
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Definition
-high attack rate among those exposed
-low attack rate among those not exposed
-most of the people who become ill should have had the exposure |
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Term
| How is relative risk interpreted? |
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Definition
| The incidence rate of disease was X time as (high/low) among exposed as the unexposed |
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Term
| When interpreting RR, what do the values mean? |
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Definition
=1 indicates no association
>1 indicates a positive association
<1 indicates a negative association |
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Term
| Assuming statistical significance, what does a relative risk of 2 mean? |
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Definition
| Exposed were twice as likely as non-exposed to be ill |
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Term
| If the RR<1 this suggests a _________factor |
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Definition
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Term
| By testing statistical significance we are determining what? |
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Definition
| how likely the study results could have occurred by chance |
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Term
| What are 3 steps to test for statistical significance? |
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Definition
-state the null hypothesis (no association between exposure and outcome)
-calculate the chi-square test
-look up corresponding p-vaule in table of chi squares |
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Term
| When interpreting p-values, epidemiologists set in advance a cutoff point above which they will consider what? What is the common cutoff point? |
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Definition
-above which they will consider chance a factor
-common cutoff is p=0.05 |
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Term
| What happens if the p-value is below the cutoff? The smaller the p value the stronger the what? |
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Definition
-if its below, the finding is considered statistically significant and the null hypothesis is rejected
-the smaller the p-value, the stronger the evidence is for statistical significance |
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Term
| In a cohort study is everyone who had the exposure known? |
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Definition
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Term
| What is the cheat/fast way to look at a table of data and determine what the causative factor is (for ex: the vanilla ice cream wedding example) without actually calculating the relative risk? |
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Definition
| -look at the highest attack rate in those that ate the specified items, then look at the lowest attack rate for those that did NOT eat the specified items. |
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Term
| In the vanilla ice cream/wedding example, the relative risk was 5.71, what does this mean? |
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Definition
| the incidence rate of GI illness was 5.7 times higher among those who ate vanilla cream compared to those who did not eat the vanilla ice cream |
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Term
| In a case control study with two groups, what defines each group? |
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Definition
| one group has the disease of interest (Cases) and a comparable group is free from the disease (controls) |
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Term
| The case control study identifies possible causes of disease by finding out what? |
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Definition
| how the two groups differ with respect to exposure to some factor |
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Term
| It is ideal to have how many controls for each case? |
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Definition
| 3 controls for every 1 case |
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Term
| What are the 4 characteristics of case-control studies: what is the point of observation? When is the outcome identified? Does it provide incidence data? Exposure is determined when ? |
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Definition
-single point of observation
-the outcome is always identified prior to the exposure
-does not directly provide incidence data
-exposure is determined retrospectively (but this is NOT considered a retrospective study)
(we are not talking about new cases, we don't know everyone who was exposed, we're just getting a pool of people with cases vs. controls) |
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Term
| What are 4 ways information about exposure status may be obtained? |
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Definition
medical records
interviews
questionnaires
surrogates such as spouses, siblings, or employers |
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Term
| In a case control study, how are we assured that the cases reflect true cases? |
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Definition
| there is a strict diagnostic criterion for the disease |
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Term
| Ideally, in a case control study, you want to identify and enroll all cases in a defined population in a specified _________/_________ |
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Definition
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Term
| The controls in a case control study should be selected from the _________/ _________as where the cases are from |
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Definition
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Term
| Three examples of people from the same population as where the cases are from that would be good controls |
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Definition
general population
hospital
family, friends, relatives |
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Term
| Why can attack rates NOT be used in case control studies? What is used instead? |
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Definition
-because the total number of people in the community who were and were not exposed is unknown
-an odds ratio is used to measure the strength of association |
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Term
| How is an odds ratio interpreted? |
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Definition
| exposure is X times (more/less) common among cases as controls |
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Term
| An odds ratio provides a good approximation of risk when what three things are present? |
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Definition
-controls are representative of a target population
-cases are representative of all cases
-the frequency of disease in the population is small |
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Term
| When using the 2x2 table, how is OR computed? |
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Definition
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Term
| When interpreting OR, what do the values mean? |
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Definition
=1 indicates no association
>1 indicates a positive association
<1 indicates a negative association |
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Term
| If you have an OR of 2, assuming statistical significance, what does this mean? |
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Definition
| cases were twice as likely as controls to be exposed |
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Term
| What does an OR <1 suggest? |
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Definition
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