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BMS1. EBM > Kraushar > Flashcards

Kraushar Flashcards

1
Q

2 X 2 tables for hypothesis testing:

(alpha, beta, and power)

A
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2
Q

Cumulative Incidence Definition and Equation:

A

(new cases) / (total population at risk over time)

  • fraction of people initially free of the outcome but who develop it over a period of time
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3
Q

Null Hypothesis (Ho):

A
  • states that there is no difference
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4
Q

Absolute risk difference =

A

Iexposed - Iunexposed

  • incidence in exposed group minus incidence in unexposed group
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5
Q

Incidence equation in steady state:

A

prevalence / duration

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6
Q

Relative risk =

A

Iexposed / Iunexposed

  • incidence in exposed group divided by incidence in unexposed group
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7
Q

Odds ratio definition and table:

A
  • retrospective
  • start with people who have disease, and go backwards to find risk factor
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8
Q

Duration equation in steady state:

A

prevalence / incidence

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9
Q

Prevalence equation in steady state:

A

(incidence) X (average duration)

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10
Q

2 X 2 tables for hypothesis testing:

(type 1 and 2 errors)

A
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11
Q

The probability of two mutually exclusive events, A or B, occurring =

A

(probability A) + (probability B)

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12
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
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13
Q

power =

A

1 - beta

  • power of study to pick up a difference when it actually does exist
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14
Q

Incidence Rate definition and equation:

A

(new cases) / (total time lapsed)

  • rate at which new disease has occurred in the population at risk per some unit time
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15
Q

Normal distribution:

A
  • classic bell curve
  • highest density in middle, tapers off on both sides
  • mean, median, and mode all in the same place (dead center of bell curve)
    • dead center for all these = perfect normal distribution (Gaussian)
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16
Q

2 X 2 tables for hypothesis testing:

(false hits and false misses)

A
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17
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
18
Q

Prevalence Definition and Equation:

A

(total cases) / (total population)

  • fraction of people experiencing a condition at a given point in time.
  • number cases right now
19
Q

Relative risk definition and table:

A
  • prospective; follow
  • start with the risk factor, follow them over time, see how many people get disease
    • everyone starts with no disease
20
Q

Probability:

A
  • a proportion in which the frequency of both events are in the denominator:

A/(A+B)

21
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
22
Q

Power depends on:

A
  • sample size (better power = more participants)
  • size of effect (better power = stronger effect)
  • subject compliance
23
Q

Sensitivity equation and table:

A

TP/(TP+FN)

SNOUT

24
Q

Standard deviation:

+/- 3SD contains –% of observations

A

99.7%

25
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
26
Q

A specific test should be utilized when:

A
  • false-positive can harm the patient physically, emotionally, or financially.
  • used to “rule-in” diagnoses when data suggest.
27
Q

Mean, median, and mode describe:

A

“central tendency”

28
Q

Aboslute risk =

A

incidence

29
Q

Standard deviation:

+/- 1SD contains –% of observations

A

68%

30
Q

Bimodal distribution:

A
  • think of breasts - there is a variable (like sex; M/F) under the bimodal curve
  • highest density at both bells, tapers off in each direction evenly
  • bimodal has two “density centers”
31
Q

The probability of two independent events, A and B, occurring together =

A

(probability A) X (probability B)

32
Q

Standard deviation:

+/- 2SD contains –% of observations

A

95%

33
Q

A sensitive test should be chosen when:

A
  • there is an important penalty for missing the diagnosis.
34
Q

mean, median, and mode location in a normal distribution:

A

overlapping dead center of the bell

35
Q

Specificity equation and table:

A

TN/(TN+FP)

SPIN

36
Q

Mean, median, and mode regarding skew:

A
  • mode insensitive (stays in bell)
  • median moderately sensitive
  • mean very sensitive (goes out to far tail)
37
Q

Right skewed distribution:

A
  • tail/outliers on the right of the bell; RIGHT TAIL
  • highest density on the left, tapers out toward the tail
  • Mode is where the bell peaks; mean is far in the tail. Median in middle.
38
Q

Left skewed distribution:

A
  • tail/outliers on the left of the bell; LEFT TAIL
  • highest density on the right (where the bell is), tapers out toward the tail
39
Q

Odds:

A
  • a ratio of the frequency of:

A to B, or A:B or A/B

40
Q

Absolute risk definition and table:

A
  • attributable risk
  • a difference of relative risks
  • how much of getting the disease is attributable to having the risk factor
41
Q

The three main criteria for abnormality:

A
  1. unusual
  2. associated with disease
  3. treatment does more harm than good

BMS1. EBM (11 decks)

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