Biostats

Question 1

case report

Answer 1

describes a particular clinical phenomenon in a single patient. Main objective of case reports and case series is to provide a comprehensive and detailed description of the case(s) under observation.

Question 2

case series

Answer 2

descriptive and do not involve hypothesis testing, but they may offer a hypothesis. Basically, case series are a series of case reports where patients had similar findings or exposure that are combined. Again, these are to help us better understand an emerging disease

Question 3

ecological study

Answer 3

Often used to look at effects of risk factors on populations. At least one variable, either an exposure or the outcome, is measured at the group (not individual) level. Examples of group-level measures include the incidence rate of a specific cancer among a specific population. The occurrence of disease is compared between groups that have different levels of an exposure. Ecological studies are useful to generate hypotheses, but should not be used to make conclusions regarding individuals within these
populations.

Question 4

ecological fallacy

Answer 4

if we make conclusions based on ecologic studies we may be ascribing to members of a group some characteristic that they in fact do not possess as individuals.

Question 5

cross sectional study

Answer 5

A study with individual-level variables that measures exposure and disease at one point in time. A snapshot of the study population. This study design provides weak evidence of causal association between exposure and outcome because we may not be certain that exposure preceded the disease. A patient survey is an example of a cross-sectional study. Gets at the question: what is happening?

Question 6

qualitative studies

Answer 6

use focus group discussions tot interviews to obtain and analyze narrative information. Can help us better understand patient experience.

Question 7

case control study

Answer 7

classify subjects by presence (case) or absence (control) of the outcome of interest. And then looks back to see how suspected exposures/risk factors might differ between the 2 groups. The unit of analysis is the exposure status.

Question 8

cohort study

Answer 8

classify subjects by presence or absence of risk factor/exposure and then look forward in time to determine the association between the risk factor/exposure (high blood pressure) and the occurrence of the outcome (Heart Attack). The unit of analysis is the outcome status.

Question 9

prospective cohort study

Answer 9

cohort study in which both determination of exposure status and occurrence of the outcome happen AFTER the beginning of the
investigation

Question 10

retrospective cohort study

Answer 10

a cohort study in which both determination of exposure status and occurrence of outcome happen BEFORE the onset of the study

Question 11

randomized controlled trials

Answer 11

enroll individuals who are randomly assigned to different groups (treatment or control) and then analyze for different outcome

Question 12

systematic reviews

Answer 12

pool results from several high-quality studies (such as randomized controlled trials) to determine a pooled effect

Question 13

crossover study design

Answer 13

enroll individuals who are randomly assigned to different groups, and then switched halfway to the other treatment (with a washout in the middle)

Question 14

exposure

Answer 14

a characteristic or occurrence suspected to be associated with the development of an outcome

Question 15

effect modulation

Answer 15

ccurs when the effect of an exposure on an outcome is modified by another variable.

Question 16

risk factor

Answer 16

something suspected of being associated with the occurrence of an outcome or disease

Question 17

relative risk

Answer 17

Risk of developing disease in the exposed group (a/a+b) divided by risk of developing disease in the unexposed group (c/c+d).

Question 18

attributable risk

Answer 18

The difference in risk between exposed and unexposed.

Question 19

case fatality rate

Answer 19

a measure of severity of a disease. Expressed as proportion of reported cases that are fatal within the population affected by the disease during a specified time.

Question 20

accumulation effect

Answer 20

patients sometimes must be exposed to a risk factor for a prolonged period of time before they develop a clinically detectable result

Question 21

absolute risk reduction

Answer 21

The difference in risk between those receiving the intervention as compared to a control.

Question 22

incidence

Answer 22

the number of new cases and it corresponds to the number of new cases of a disease diagnosed in a population within a given time period. Calculation # of new cases/# of people at risk

Question 23

prevalence

Answer 23

all current cases or all of the cases at a given time (new and old) and refers to
the total number of diseased individuals in a population

Question 24

measurement or information bias

Answer 24

systematically overstates or understates the true value when the method for obtaining information about the risk factor or the outcome is inadequate resulting in inaccurate data. Or when the method DIFFERS between the 2 study groups.

Question 25

recall bias

Answer 25

occurs when there is reason to suspect that information
obtained by asking subjects about their past is likely to differ systematically between the groups

Question 26

nonresponse and loss to follow-up bias

Answer 26

when you can’t obtain data from study subjects regarding outcomes and possible confounders because they refuse to respond to questions or cannot be contacted

Question 27

selection bias

Answer 27

a systematic error in the study resulting from the way in which subjects were selected for inclusion in the study.

Question 28

observer-expectancy bias

Answer 28

when a research (intentionally or unintentionally) changes the outcome of a treatment because of their belief that it will work.

Question 29

confounding

Answer 29

when an association between risk factor A and the outcome is deemed to be causal but it is in fact due to the presence of risk factor B, that is associated with both factor A and the outcome.