Lectures 1-4 Flashcards

1
Q

Definition of EBM:

A
  • medicine combining the best current research evidence with clinical expertise and patient values.
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2
Q

The five outcomes of disease:

A
  1. death
  2. disease
  3. discomfort
  4. disability
  5. dissatisfaction
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3
Q

Prevalence =

A

(total #sick)/(total population)

  • how many people are sick
  • a single time point
  • Prevalence can be used to estimate the likelihood of a diagnosis before any “tests”
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4
Q

Cumulative incidence:

A

(new cases)/(total population at risk at study start)

  • how many people are getting sick (NEW CASES)
  • incidence is a rate, it happens over a time interval
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5
Q

Incidence density =

A
  • the incidence rate in a dynamic, changing population in which people are under study and at risk for varying periods of time.
  • “person-years” or “person-days”
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6
Q

Incidence equation in steady state:

A

prevalence / duration

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7
Q

Duration equation in steady state:

A

prevalence / incidence

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8
Q

Prevalence equation in steady state:

A

(incidence) X (average duration)

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9
Q

Apparent incidence depends on:

A
  • intensity of effort to identify cases, not just the true underlying incidence.
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10
Q

Epidemic:

A
  • an increase in incidence of a disease in a community or region.
  • Outbreak is sometimes used to mean a small epidemic in a limited location.
  • An epidemic curve is a plot of the distribution of cases over time.
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11
Q

Pandemic:

A
  • an epidemic that crosses many international boundaries.
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12
Q

Endemic:

A
  • the constant presence of a disease or infectious agent within a given geographic area or population group.
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13
Q

Random samples:

A
  • Every person has an equal probability of being sampled
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14
Q

Probability sample:

A
  • Every person has a known (but not necessarily equal) probability of being selected.
  • Can weight the sample towards some low-frequency groups of interest.
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15
Q

“grab” samples:

A
  • convenient
  • susceptible to bias
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16
Q

alpha =

A
  • the probability you’ll make a false hit.
  • Arbitrarily, p = 0.05
  • false hit = type 1 error
  • 5% of the time, we’ll make an error
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17
Q

beta =

A
  • probability you won’t find a difference when one actually exists (false miss)
  • false miss = type 2 error
  • probability of missing a reality
18
Q

power =

A

1 - beta

  • power of study to pick up a study when it actually does exist
  • Low power is a common reason for type II errors.
19
Q

Low power is a common reason for what types of errors?

A

type 2

20
Q

Power can be reduced by:

A

BLAMSE

  1. beta too lax (~0.2)
  2. low prevalence of outcome in population
  3. alpha too stringent (~ 0.01)
  4. multiple comparison adjustments
  5. sample size (small)
  6. effect size (small)
21
Q

A confidence interval is:

A
  • the range of values you get for repeated/multiple samples
  • 95% CI means that 95% of values fall within 2SD
22
Q

2 X 2 tables for hypothesis testing:

(alpha, beta, and power)

A
23
Q

2 X 2 tables for hypothesis testing:

(type 1 and 2 errors)

A
24
Q

2 X 2 tables for hypothesis testing:

(false hits and false misses)

A
25
Q

95% CI equation:

A

95% CI = mean +/- 1.96(SEM)

  • SEM = SD/ √n
26
Q

Standard error of the mean (SEM) eqaution:

A

SEM = SD/ √n

  • SD = standard deviation
  • n = sample size
27
Q

In order to be signficant, confidence intervals cannot:

A
  1. cannot overlap / touch
  2. cannot include 0 when doing correlations
  3. cannot include 1 when relative risk, hazards ratio, odds ratio
28
Q

When to use T-test:

A
  • use when comparing means of 2 groups
  • PARAMETRIC
29
Q

Mann-Whitney test:

A
  • non-parametric test similar to t-test
  • does not rely on mean or variation
30
Q

Risk can be offset by:

A
  1. Intervention
  2. Treatment
  3. Prevention
  4. Education
31
Q

A risk factor is:

A
  • anything which increases the likelihood that a disease will occur
  • can be genetic or environmental
32
Q

The three types of prevention:

A
  1. Primary: before exposure (PREVENT)
  2. Secondary: after exposure (SCREEN)
  3. Tertiary: after disease process occurs (TREAT)
33
Q

Primary prevention:

A
  • before exposure
  • prevent disease occurrence
    • e.g. vaccinations
34
Q

Secondary prevention:

A
  • after exposure
  • screening early for disease
    • e.g. pap smears
35
Q

Tertiary prevention:

A
  • after disease process
  • treat
    • e.g. chemotherapy
36
Q

When to use ANOVA:

A
  • when comparing means of 3 or more groups
37
Q

Pathogenic triangle:

A
  • host — environment — agent (all are connected in an exposure)
38
Q

Latency:

A
  • Time between exposure and event
39
Q

Null Hypothesis (Ho):

A
  • states that there is no difference
40
Q

Type I error:

A
  • FALSE POSITIVE
    • saying there is a difference when there is not.
    • rejecting the null hypothesis when it should be accepted
41
Q

Type II error:

A
  • FALSE NEGATIVE
    • saying there is no difference in treatment effects when there is.
    • failing to reject (accepting) the null hypothesis when it should be rejected
42
Q

How to increase the power of a study:

A
  • increase the number of subjects