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Step 1 Crush 250! - Hans > Biostats > Flashcards

Biostats Flashcards

1
Q

study type that can show risk factor association without establishing causality?

A

cross sectional study

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2
Q

odds ratio is used in what type of study?

A

case control

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3
Q

triple blind refers to

A

the additional blinding of the researchers analyzing the data

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4
Q

which phase of clinical trial assess efficacy, optimal dosing, and adverse effects?

A

phase II

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5
Q

what is equivalent to 1 - false negative rate?

A

sensitivity

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6
Q

what is another name for sensitivity?

A

true positive rate

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7
Q

explain how PPV and NPV are affected by pretest probability?

A

high pretest probability leads to

  1. high PPV
  2. low NPV
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8
Q

pretest probability is equivalent to

A

prevelance

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9
Q

equation for odd ratio?

A

ad/bc

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10
Q

equation for relative risk?

A

a/(a+b) / c/(c+d)

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11
Q

equation for the attributable risk?

A

incidence in exposed - incidence in non exposed = a/(a+b) - c/(c+d)

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12
Q

equation for the relative risk reduction (RRR) ?

A

RRR = 1 - RR

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13
Q

equation for absolute risk reduction (ARR) ?

A

c/(c+d) - a/(a+b)

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14
Q

equation for number needed to treat (NNT)?

A

NNT = 1/ARR

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15
Q

equation for number needed to harm (NNH)?

A

NNH = 1/AR

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16
Q

3 terms that are equivalent to “precision?”

A

consistency, reproducibility, reliability

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17
Q

2 terms that are equivalent to “accuracy?”

A

trueness, validity

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18
Q

how does increasing precision affect standard deviation and statistical power (1-B)?

A
  1. dec standard deviation

2. inc statistical power (1-B)

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19
Q

what is Berkson bias?

A

example of selection bias, study population selected from hospital is less healthy than general propulation

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20
Q

what is Pygmaliion effect?

A

researcher’s belief in the efficacy of a treatment changes the outcome of that treatment

21
Q

in positive skew distribution, explain the relationship of mean, median, mode?

A

mean > median > mode

22
Q

what statistical hypothesis do you use when there is some association between the dz and the risk factor in the population?

A

alternative (H1)

23
Q

what is a type I error?

A

alpha, incorrectly rejecting the null hypothesis (when null hypothesis is true)

24
Q

type I error is also known as

A

false-positive error

25
Q

what is type 2 error?

A

beta, not rejecting the null hypothesis when it should have been rejected

26
Q

what part of medicare pays for hospital insurance?

A

part A

27
Q

what disease prevention identifies pts at risk of unnecessary treatment protecting from the harm of new interventions?

A

Quaternary

28
Q

example of primary dz prevention?

A

HPV vaccination

29
Q

example of secondary dz prevention?

A

PAP smear

30
Q

example of tertiary dz prevention?

A

chemotherapy

31
Q

what is statistical power?

A

1 - type II error (beta)

32
Q

what are 3 ways to improve power?

A
  1. inc sample power
  2. inc expected effect size
  3. inc precision of measurement
33
Q

type II error is also known as

A

false-negative error

34
Q

explain the relationship of mean, median, mode in negative skew

A

mean

35
Q

what is the strategy to reduce lead-time bias?

A

measure back-end survival (adjust survival according to the severity of dz at the time of diagnosis)

36
Q

what are the 2 examples of bimodal distribution?

A

Hodgkin lymphoma, suicide rate by age

37
Q

1 - false positive rate?

A

specificity

38
Q

what is another name for specificity?

A

true negative rate

39
Q

which phase of the clinical trial tests pharmacodynamics/pharmacokinetics?

A

phase I

40
Q

which type of study can be either prospective or retrospective?

A

cohort

41
Q

which type of study can make a statement such as “pts with COPD had higher chance of a hx of smoking than those w/o COPD.”

A

case control

42
Q

which type of study can make a statement such as “smokers had a higher risk of developing COPD than nonsmokers.”

A

cohort

43
Q

what decreases precision in a test?

A

random error

44
Q

what decreases accuracy in a test?

A

systemic error

45
Q

what portion of a population belongs to +/- 1 standard deviation?

A

68%

46
Q

what portion of a population belongs to +/- 2 standard deviation?

A

95%

47
Q

what portion of a population belongs to +/- 3 standard deviation?

A

99.7%

48
Q

what Z value is used for 95% CI?

A

1.96

49
Q

what Z value is used for 99% CI?

A

2.58

Step 1 Crush 250! - Hans (41 decks)

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