Handout Review Flashcards

1
Q

The number of occurrences at ONE PARTICULAR TIME

A

Prevalence

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2
Q

The occurrence, RATE, or frequency of a disease

A

Incidence

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3
Q

???

A

Outlier

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4
Q

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)

A

Correlation coefficient

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5
Q

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

A

Relative Risk

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

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6
Q

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

A

Relative risk

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7
Q

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

A

Sensitivity

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8
Q

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

A

sensitivity

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9
Q

The proportion of people without disease who have a negative test

A

specificity

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10
Q

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

A

specificity

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11
Q

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

A

Two-stage (sequential) testing

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12
Q

Loss in net sensitivity, gain in net specificity

A

Two-stage (sequential) testing

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13
Q

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

Pt considered negative if they test neg on both.

A

Simultaneous testing

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14
Q

Net gain in sensitivity, net loss in specificity

A

Simultaneous testing

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15
Q

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

A

External validity

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16
Q

Also called generalizability

A

External validity

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17
Q

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

A

Internal validity

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18
Q

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

A

confidence interval

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19
Q

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

A

Confidence interval

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20
Q

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…

A

Confidence interval

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21
Q

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

A

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.

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22
Q

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

A

number needed to treat (NNT)w

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23
Q

Expresses the likelihood of the tx to benefit an individual patient

A

number needed to treat (NNT)

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24
Q

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

A

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)

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25
When an experimental treatment is detrimental, what term would we employ?
number needed to harm (NNH) Numbers are similar to NNT, except NNH will have a negative absolute risk reduction
26
Low probability of a false negative?
Sensitivity
27
Highly useful when negative because it rules out the disease
Sensitivity
28
Low probability of a false positive
specificity
29
Highly useful when it is positive because it tends to rule in the disease
Specificity
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
Intention to treat analysis | note that this was taken from the book the definition couldn't be found in the slides
31
Indicates the chance of a random error
p-value
32
P-value key metrics?
p = or < .05 (statistically significant) p < .001 (HIGHLY significant)
33
When a drug/procedure/intervention works under ideal circumstances
efficacy
34
When we reject the null hypothesis, but the hypothesis is actually true?
Type 1 error aka Alpha error
35
When we fail to reject the null hypothesis, but the null hypothesis is false
Type 2 error aka Beta error
36
variables that correlate directly or indirectly with the dependent and independent variables
Confounding variables
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
confounding variable
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
case report
39
Descriptive study of individual cases that share a commonality
case series
40
Case series are used to?
Examine adverse events/effects Catalog new diseases/outbreaks Determine feasibility/safety of new tx/intervention Discuss potential efficacy of new tx
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
Case control studies Researcher looks back to identify factors/exposures that might be associated with illness
42
Tries to capture the cause and effect relationship by comparing frequency of a risk factor among those who are exposed and not exposed
Case-control studies
43
thorough, comprehensive, and explicit way of interpreting the medical literature
systematic review
44
STATISTICAL approach to combine the data derived from several seleted studies
meta-analysis
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
prospective cohort studies
46
Strongest observational study?
cohort study
47
Strengths of cohort study?
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
48
Highest validity of observational study design?
Cohort study
49
Cross sectional
An analytic, observational study examines relationship between otucomes and other variables of interest as they exist in a defined population at one partcular time
50
Can a cross-sectional determine prevalence?
Yes, but it cannot show causality nor a temporal relationship
51
Cross sectional strengths/
assess multiple outcomes and exposures simultaneously can be completed quickly data generated can lead to further studies can generate prevalence
52
Cross sectional weaknesses?
no time reference (snapshot in time) only useful for common conditions cannot calculate incidence Results are dependent on study population
53
Main purpose of randomization is to?
prevent any potential biases on the part of the investigators
54
Though randomization strives for comparability, it is not....?
guaranteed
55
The gold standard?
Double blinded randomized control trial
56
Limitations of control studies?
Large trials (may effect statistical power) Long term follow up (possible losses) Compliance Expensive Possible ethical questions
57
Quasi experimental study aka?
non-randomized control trial
58
Limitations of non-randomized control trials?
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)
59
Variant of case-control study Each case becomes their own individual control Used for transient exposures during a discrete occurence?
Case crossover study
60
Must have a washout period?
Case crossover study
61
Intention to treat?
Analyzed according to original randomized assignment If bias occurs, typically biases towards the null; provides a more conservative estimate
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
qualitative research
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)
manifest level
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)
Latent level
65
the score that occurs most frequently
mode Measure of central tendency
66
middle point
median Measure of central tendency
67
the average
mean Measure of central tendency
68
least precise measure of central tendency?
mode
69
percent of patients with positive test who actually have the disease
positive predictive value
70
assesses reliability of positive test
positive predictive value
71
Percentage of patients with a negative test who actually do NOT have the disease
negative predictive value
72
assesses reliability of a negative test
negative predictive value
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
lower increase less
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
higher decreased more
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.
Likelihood ratio (LR)
76
provides indication of the test’s discriminatory power
Likelihood ratio (LR)
77
Low prevalence = Less reliable positive test result; therefore, use ___
Likelihood ratio (LR)
78
LR addresses ?
How much more likely are we to find that a test is positive among patients with disease compared with those without disease?
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).
How good the test is at “Ruling in” disease!
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)
How good the test is at “Ruling out” disease
81
Measures the strength of association between an exposure and disease
Odds ratio (OR)
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
Odds ratio (OR)
83
strives for comparability of the different treatment groups; however, its not guaranteed
randomization
84
the best approach in the design of a trial, and the critical element of ______ is the unpredictability of the next assignment
randomization
85
occurs when relationships that exist for groups are assumed to also be true for individuals
ecological fallacy | type of bias
86
"When investigators know the identity of case and comparison subjects and which exposures are risks, objectivity is put to a strenuous test"
Researcher bias | from book pg 47
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?
Researcher bias | from book pg 47
88
Both are used for the development of Clinical Practice Guidelines (CPGs)?
Meta analysis Systematic review
89
What is the difference between a "systematic review" and a "meta-analysis"?
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
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
epidemiology
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
biostatistics