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uworld > BIOSTATS > Flashcards

BIOSTATS Flashcards

1
Q

wider CI is most likely due to what

A

smaller sample size

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2
Q

RR 2.0, CI (1.2-2.8) - is this statistically significant

A

yes - b/c does not include 1

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3
Q

95% of study data will lie b/w how many standard deviations from the mean

A

2 SD from the mean

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4
Q

99.7% of study data will fall b/w how many standard deviation form mean

A

3 SD from the mean

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5
Q

68% of study dad will fall b/w how many SD of the mean

A

1 SD of mean

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6
Q

if the test is negative - what is the probability that the patient will have the disease

A

1 - negative predictive value

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7
Q

cofounding bias

A

bias that results when the exposure disease relationship is mixed with the effect of extraneous factors

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8
Q

what study can have recall bias

A

retrospective study

- case control studies

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9
Q

chi-squared - when to use

A

when comparing the proportions of a categorized outcome

2x2 table ( ex: HRT vs. no HRT)

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10
Q

when to use two sample x test

A

two MEANS not proportions

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11
Q

when to use two sample T test

A

To compare two means NOT proportions

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12
Q

when to use ANOVA

A

compare MEANS of 3 or more variables

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13
Q

Meta-analysis

A

spidemiologic method of pollen the data from several studies to do an analysis having a relatively big statical power

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14
Q

what does it mean to say randomization was successful

A

means that the baseline characteristics of the patients were the same b/w treatment and placebo gourds

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15
Q

NNT

A

1-ARR

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16
Q

hawthorne effect

A

tendency of the study population to affect the outcome since they are aware that they are being studied

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17
Q

incidence

A

number of new cases of disease that develops in a specific population over a specified time period

18
Q

prevalence

A

existing case of disease in population at a particular point in time

Prevalence = incidence x duration of disease

19
Q

increase in prevalence but same incidence - what can cause this?

A
  • attributed to factors that prolong duration of disease

ex> improved quality of care and disease management

20
Q

case control studies help to control what type of bias

A

confounding

21
Q

what is an efficient method to control confounding

A

matching - patients selected with same age, race and are used as control

  • used in CASE CONTROL STUDIES
22
Q

what study is the best to pick up incidence of disease

A

COHORT

23
Q

retrospective cohort

A

population with disease

Compares disease incidence with and without a risk factor

24
Q

what study type looks at prevalence

A

Cross sectional

25
Q

What study looks at risk factor frequency

A

Case control

Diseased cases and non disease controls - looks at risk factor frequency

26
Q

methods to control cofounding

A

Design Stage:

  • MATCHING
  • RESTRICTION (limiting study participation to individuals with specific characteristics i.e.: only men
  • RANDOMIZATION

Analysis Stage
- stratified analysis
Statistical modeling

27
Q

post hoc analysis

A

performing unplanned statistical test on patterns that were identified after the fact in the data after completed study

28
Q

effect modification

A

results when an external variable positively or negatively impacts the effect of risk factor on the disease

Ex: estrogen treatment increase risk of VTE and this effect is augmented by smoking

29
Q

factorial design studies

A

randomization to different interventions with additional study of 2 or more variables

30
Q

cross over study

A

one group patients - get treatment A

Other group of patients get treatment B

Then they cross over

31
Q

Attributable risk percent or etiologic fraction

A

ARP = risk in exposed - risk in unexposed / risk in exposed

32
Q

rr 4.0 95% CI 1.5 - 6.5

The risk of getting disease 4Xmore with alcohol than in people without using alcohol

what is the precent of disease in people who drink alcohol

A

They want you to calculate ARP (attributable risk percent)

ARP = 4-1/4 = 0.75%

33
Q

generalizability or external validity

A

applicability of the study results to other populations

34
Q

median

A

blue located in the middle of dataset

35
Q

mean

A

all numbers added together an then divided by the number of numbers

36
Q

mode

A

the most frequent number in data set

37
Q

smoking and alcohol as cofounders

A

smoking should be related to alchol comsumption

38
Q

tighter CI - means

A

the more precise the results

39
Q

mode of inheritance for hemophilia A

A

X linked recessive disorder

40
Q

two sample t test vs. two sample x test

A

Two sample t test - compares two means

Two sample z test - compares two means but population ( not sample) - since population variance is not usually known - test has limited applicability

uworld (11 decks)

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