Handout Review

Question 1

The number of occurrences at ONE PARTICULAR TIME

Answer 1

Prevalence

Question 2

The occurrence, RATE, or frequency of a disease

Answer 2

Incidence

Question 3

???

Answer 3

Outlier

Question 4

Represented by “r” (rho)

The closer to 1 (or -1) the stronger the relationship. Closer to 0? A weaker relationship.

Pearson correlation is the most common but sensitive to outliers (can be misleading if non-linear relationship)

Answer 4

Correlation coefficient

Question 5

Measures magnitude of an association between an exposed and non-exposed (control) group

Calculated using cumulative incidence data to measure the probability of developing disease

Answer 5

Relative Risk

Must have incidence information (cohort of clinical trials are conducted over time)

Question 6

Basic risk statements express the likelihood that a particular event will occur within a particular population

Identifies what in our environment can lead to beneficial or adverse medical outcomes

Answer 6

Relative risk

Question 7

Proportion of people with the disease who have a positive test for the disease

Answer 7

Sensitivity

Question 8

The ability of the test to identify correctly those who have the disease

Answer 8

sensitivity

Question 9

The proportion of people without disease who have a negative test

Answer 9

specificity

Question 10

Ability of the test to identify correctly those who don’t have the disease

Answer 10

specificity

Question 11

In this screening, a less expensive/invasive/uncomfortable test is generally performed first… those that screen positive are recalled for further testing with more expensive/invasive/uncomfortable test

Answer 11

Two-stage (sequential) testing

Question 12

Loss in net sensitivity, gain in net specificity

Answer 12

Two-stage (sequential) testing

Question 13

Patient is considered positive if they test pos on either/both tests.

Pt considered negative if they test neg on both.

Answer 13

Simultaneous testing

Question 14

Net gain in sensitivity, net loss in specificity

Answer 14

Simultaneous testing

Question 15

ability to apply results obtained from a study population to a broader population

Answer 15

External validity

Question 16

Also called generalizability

Answer 16

External validity

Question 17

Within the confines of the study, the results appear to be accurate and the interpretation of the investigators is supported

Answer 17

Internal validity

Question 18

Most valuable in determining the statistical significance of an effect estimate?

Answer 18

confidence interval

Question 19

More important than p-value? A better determination of significance?

Answer 19

Confidence interval

Question 20

Produces a range within which the true value most likely lies…

“We be 95% certain that the true value is within the __ range”

Narrower is better…

Answer 20

Confidence interval

Question 21

Odds ratios calculated in a case-control study are a good approximation of relative risk in the population when what three conditions are met?

Answer 21

When cases studied are representative, with regard to history of exposure, of all people w/ the disease in the population from which the cases were drawn.

When CONTROLS studied are representative, with regard to history of exposure, of all people w/ the disease in the population from which the CONTROLS were drawn.

When the studied disease doesn’t occur frequently.

Question 22

The number of patients who need to receive the new intervention instead of the standard alternative in order for ONE additional patient to benefit

Answer 22

number needed to treat (NNT)w

Question 23

Expresses the likelihood of the tx to benefit an individual patient

Answer 23

number needed to treat (NNT)

Question 24

Is there an absolute value for NNT that defines whether something is effective or not?

Answer 24

No. But NNTs for very effective treatments are usually in the range of 2-4.

Usually a lower number b/c we expect large effects in small numbers of people.

Larger NNTs can be found useful where few pts are affected in large populations (use for prophylactic measures)

Question 25

When an experimental treatment is detrimental, what term would we employ?

Answer 25

number needed to harm (NNH) Numbers are similar to NNT, except NNH will have a negative absolute risk reduction

Question 26

Low probability of a false negative?

Answer 26

Sensitivity

Question 27

Highly useful when negative because it rules out the disease

Answer 27

Sensitivity

Question 28

Low probability of a false positive

Answer 28

specificity

Question 29

Highly useful when it is positive because it tends to rule in the disease

Answer 29

Specificity

Question 30

Means that subjects are analyzed according to the categories into which they were originally randomized. Even if subjects withdraw/fail to take prescribed/otherwise adjust their tx, they still belong to their original tx group

Answer 30

Intention to treat analysis | note that this was taken from the book the definition couldn't be found in the slides

Question 31

Indicates the chance of a random error

Answer 31

p-value

Question 32

P-value key metrics?

Answer 32

p = or < .05 (statistically significant) p < .001 (HIGHLY significant)

Question 33

When a drug/procedure/intervention works under ideal circumstances

Answer 33

efficacy

Question 34

When we reject the null hypothesis, but the hypothesis is actually true?

Answer 34

Type 1 error aka Alpha error

Question 35

When we fail to reject the null hypothesis, but the null hypothesis is false

Answer 35

Type 2 error aka Beta error

Question 36

variables that correlate directly or indirectly with the dependent and independent variables

Answer 36

Confounding variables

Question 37

AKA hidden variable, lurking variable An extraneous variable in a statistical model that correlates (positively or negatively) with both the dependent and independent variable

Answer 37

confounding variable

Question 38

A descriptive study that provides a narrative in professional literature that IDs a single incident and discusses pertinent factors related to that patient Brings a nove/unusual patient to the attention of colleagues

Answer 38

case report

Question 39

Descriptive study of individual cases that share a commonality

Answer 39

case series

Question 40

Case series are used to?

Answer 40

Examine adverse events/effects Catalog new diseases/outbreaks Determine feasibility/safety of new tx/intervention Discuss potential efficacy of new tx

Question 41

An analytic/observational study Studies in which pts who already have a specific condition are compared with people who do not have the condition

Answer 41

Case control studies Researcher looks back to identify factors/exposures that might be associated with illness

Question 42

Tries to capture the cause and effect relationship by comparing frequency of a risk factor among those who are exposed and not exposed

Answer 42

Case-control studies

Question 43

thorough, comprehensive, and explicit way of interpreting the medical literature

Answer 43

systematic review

Question 44

STATISTICAL approach to combine the data derived from several seleted studies

Answer 44

meta-analysis

Question 45

identify a group of patients who are already taking a particulat tx/have an exposure, follow them forward over time and then compare their outcomes with a similar group that has not been affected by the treatment or exposure being studied

Answer 45

prospective cohort studies

Question 46

Strongest observational study?

Answer 46

cohort study

Question 47

Strengths of cohort study?

Answer 47

study multiple effects of a single exposure identify a temporal relationship b/w exposure/outcome help confirm casue/effect and magnitude of effect can measure incidence of dz can calculate relative risk

Question 48

Highest validity of observational study design?

Answer 48

Cohort study

Question 49

Cross sectional

Answer 49

An analytic, observational study examines relationship between otucomes and other variables of interest as they exist in a defined population at one partcular time

Question 50

Can a cross-sectional determine prevalence?

Answer 50

Yes, but it cannot show causality nor a temporal relationship

Question 51

Cross sectional strengths/

Answer 51

assess multiple outcomes and exposures simultaneously can be completed quickly data generated can lead to further studies can generate prevalence

Question 52

Cross sectional weaknesses?

Answer 52

no time reference (snapshot in time) only useful for common conditions cannot calculate incidence Results are dependent on study population

Question 53

Main purpose of randomization is to?

Answer 53

prevent any potential biases on the part of the investigators

Question 54

Though randomization strives for comparability, it is not....?

Answer 54

guaranteed

Question 55

The gold standard?

Answer 55

Double blinded randomized control trial

Question 56

Limitations of control studies?

Answer 56

Large trials (may effect statistical power) Long term follow up (possible losses) Compliance Expensive Possible ethical questions

Question 57

Quasi experimental study aka?

Answer 57

non-randomized control trial

Question 58

Limitations of non-randomized control trials?

Answer 58

Study group characteristics may not be balanced at baseline and these differences may confoudn study's results (typical confounding variables include age, educational level, motivation, severity of illness, socioeconomic status/income, comorbidities)

Question 59

Variant of case-control study Each case becomes their own individual control Used for transient exposures during a discrete occurence?

Answer 59

Case crossover study

Question 60

Must have a washout period?

Answer 60

Case crossover study

Question 61

Intention to treat?

Answer 61

Analyzed according to original randomized assignment If bias occurs, typically biases towards the null; provides a more conservative estimate

Question 62

Research dealing with phenomena that that are difficul or imposible to quantify mathematically, such as beliefs, meanings, attributes, and symbols; it may invovle content analysis

Answer 62

qualitative research

Question 63

Basic level: a descriptive account of the date i.e., this is what was said but no comments or theories as to why or how (regarding qualitative research)

Answer 63

manifest level

Question 64

higher level; a more interpretive analysis that is concerned with the response as well as what may have been implied or inferred (regarding qualitative research)

Answer 64

Latent level

Question 65

the score that occurs most frequently

Answer 65

mode Measure of central tendency

Question 66

middle point

Answer 66

median Measure of central tendency

Question 67

the average

Answer 67

mean Measure of central tendency

Question 68

least precise measure of central tendency?

Answer 68

mode

Question 69

percent of patients with positive test who actually have the disease

Answer 69

positive predictive value

Question 70

assesses reliability of positive test

Answer 70

positive predictive value

Question 71

Percentage of patients with a negative test who actually do NOT have the disease

Answer 71

negative predictive value

Question 72

assesses reliability of a negative test

Answer 72

negative predictive value

Question 73

If you have a low prevalence of disease, in regards to positive predictive value, you'll have ___ PPV, your false positive ____, and its a ___ reliable positive test result

Answer 73

lower increase less

Question 74

If you have a low prevalence of disease, in regards to negative predictive value, you'll have ___ NPV, your false negative ____, and its a ___ reliable negative test result

Answer 74

higher decreased more

Question 75

Summarizes the same kind of information sensitivity and specificity and can be used to calculate the probability of disease in a low prevalence setting.

Answer 75

Likelihood ratio (LR)

Question 76

provides indication of the test’s discriminatory power

Answer 76

Likelihood ratio (LR)

Question 77

Low prevalence = Less reliable positive test result; therefore, use ___

Answer 77

Likelihood ratio (LR)

Question 78

LR addresses ?

Answer 78

How much more likely are we to find that a test is positive among patients with disease compared with those without disease?

Question 79

A positive LR (LR+) is the ratio of the proportion of diseased people with a positive test result (sensitivity) to the proportion of non-diseased people with a positive result (1-specificity).

Answer 79

How good the test is at “Ruling in” disease!

Question 80

A negative LR (LR-) is the proportion of diseased people with a negative test result (1-sensitivity) divided by the proportion of non-diseased people with negative test results (specificity)

Answer 80

How good the test is at “Ruling out” disease

Question 81

Measures the strength of association between an exposure and disease

Answer 81

Odds ratio (OR)

Question 82

If exposure does not affect (either cause or protect from) disease, the OR is ~ 1 If the exposure is related to the disease, the OR > 1 If the exposure is protective against the disease, the OR < 1

Answer 82

Odds ratio (OR)

Question 83

strives for comparability of the different treatment groups; however, its not guaranteed

Answer 83

randomization

Question 84

the best approach in the design of a trial, and the critical element of ______ is the unpredictability of the next assignment

Answer 84

randomization

Question 85

occurs when relationships that exist for groups are assumed to also be true for individuals

Answer 85

ecological fallacy | type of bias

Question 86

"When investigators know the identity of case and comparison subjects and which exposures are risks, objectivity is put to a strenuous test"

Answer 86

Researcher bias | from book pg 47

Question 87

Searching medical records more thoroughly or questioning more diligently about exposure to medical asbestos in cases of fibrotic lung disease or about the consumption of artificial sweeteners among bladder patients... an example of?

Answer 87

Researcher bias | from book pg 47

Question 88

Both are used for the development of Clinical Practice Guidelines (CPGs)?

Answer 88

Meta analysis Systematic review

Question 89

What is the difference between a "systematic review" and a "meta-analysis"?

Answer 89

A “systematic review” is a thorough, comprehensive, and explicit way of interpreting the medical literature A "meta-analysis" is a statistical approach to combine the data derived from several selected studies

Question 90

is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control health problems

Answer 90

epidemiology

Question 91

the branch of statistics that deals with data relating to living organisms Using the tools of statistics to help answer pressing research questions in medicine, biology, and public health

Answer 91

biostatistics