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NAPLEX 21 > BIOSTATS concepts > Flashcards

BIOSTATS concepts Flashcards

1
Q

The type of data has a logical order with VALUES that continuously increase (or decrease) by the SAME amount

example: heart rate of 120BPM is twice as fast as a HR of 60BPM

A

continuous data

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2
Q

What are the two types of continuous data?

A

interval data and ratio data

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3
Q

What is the difference between interval and ratio data?

A

interval data has NO meaningful zero

example: celsius temperature, it has no meaningful zero (0 does not mean no temperature)

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4
Q

What is an example of ratio data?

A

meaningful zero –

HR of 0BPM is cardiac arrest, zero equals none

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5
Q

What are the two types of categorical/discrete data?

A

nominal and ordinal

*these are categories!

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6
Q

in this type of data, subjects are sorted into arbitrary categories (names) such as male and female. “yes or np” data

A

nominal

name=nominal

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7
Q

This type of data comes from the word order - this data is ranked and has a logical order

example: pain scale (2 does not mean twice less than score 4)
these categories do NOT increase by the same amount

A

ordinal dat

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8
Q

Data is provided by some type of measurement which has unlimited options (theoretically) of continuous values

A

continuous data

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9
Q

Data fits into a limited number of categories

A

discrete/categorical data

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10
Q

Examples: age, height, weight, time, blood pressure

A

ratio data
(continous data)

ordered, equal

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11
Q

Example: temperature scales

A 
interval data
(continuous data)

ordered, equal

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12
Q

Example: gender, ethnicity, martial status, mortality

A

nominal data

no set order

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13
Q

Example: NYHA functional Class I-IV, pain scale 0-10

A

ordinal data

ordered, ranked

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14
Q

the average value

A

mean

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15
Q

what type of data is mean more preferred for?

A

continuous data that is normally distributed

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16
Q

the value in the middle when the values are arranged from lowest to highest

A

median

preferred for ordinal data or continuous data that is SKEWED

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17
Q

The value that occurs most frequently

A

mode

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18
Q

what measure of central tendencyy is preferred for nominal data?

A

mode

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19
Q

what measure of central tendencyy is preferred for ordinal data or continuous data that is SKEWED?

A

median

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20
Q

the difference between the highest and lowest values

A

range

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21
Q

indicates how spread out the data is

A

standard deviation

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22
Q

Large sample sets of what type of data forms a bell curve?

A

continuous

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23
Q

what does the distribution of data that is normal/bell shape look like?

A

symmetrical (even on both sides) with most of the values closer to the middle

half of the values are on the left side of the curve
half of the values are on the right side
with small number of values on the tails

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24
Q

When data is normally distributed what does the mean median and mode look like?

A

the same!

68% of the values fall within 1 SD of the mean and 95% of the values fall within 2SDs of the mean

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25
Q

When the data narrows what happens to the curve?

A

the curve gets taller and skinnier

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26
Q

When does skewed data normally happen?

A

sample size is small and there are outliers

right skew - more low values
left skew - more high values

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27
Q

an outlier has a large impact on the (median mean mode)?

A

mean

in this case, median is a BETTER measure of central tendency

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28
Q

The distortion of central tendency caused by outliers is decreased by..

A

collecting more values

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29
Q

In a study, does a researcher want to accept the null or the alternate hypothesis?

A

the alternate!

null=no statistically significant difference

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30
Q

___ is the threshold for rejecting the null hypothesis

A

alpha

a maximum permissible error margin (commonly set at 5% or 0.05)

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31
Q

Where does alpha correlate with when the data has normal distribution?

A

the values in the tails

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32
Q

what value is compared to alpha?

A

the p-value

if the alpha is set at 0.05 and the p value is less than alpha (P<0.05) the null hypothesis is rejected

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33
Q

_______ provides the same information about significance as the p-value, plus the precision of the result

A

confidence interval

alpha and the CI in a study will correlate with each other

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34
Q

if alpha is 0.05, the study reports __% CIs

A

95%

alpha = 0.01, CI=99%

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35
Q

Comparing difference data, when is it significant?

A

when the CI doesn’t cross ZERO

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36
Q

comparing ratio data (relative risk, odds ratio, hazard ratio) is significant when..

A

the CI doesn’t cross ONE

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37
Q

Relative risk crosses one. is it significant?

A

no!

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38
Q

odds ratio crosses zero, is it significant?

A

yes! it doesn’t cross one@

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39
Q

hazard ratio crosses one is it significant?

A

no!

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40
Q

What does a narrow CI range imply?

A

HIGH precision

wide CI range = poor precision

The CI indicate that you are 95% confident that the true value of the ARR for the general population lies somewhere in the RANGE (0.95 CI 0.06-0.35)

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41
Q

What is a type-I error?

A

false positive

the alternate hypothesis was accepted and the null hypothesis was rejected in ERROR

42
Q

the probability or risk of making a type I error is determined by

A

alpha

and it relates to the confidence interval

CI= 1-alpha

43
Q

When alpha is 0.05 and a study is reported with a P<0.05, what is the probability of a type I error occurring?

A

<5%

1-0.05 = 0.95 = 95% CI

44
Q

What is a type II error?

A

false negative! this one sucks!!!!!!!!

when the null hypothesis is ACCEPTED when it should have been REJECTED :(

45
Q

___ is set by the investigators during the design of a study, and it is typically set at 0.1 or 0.2, meaning the risk of a type II error is 10% or 20%

A

BETA!

beta related to POWER

46
Q

The risk of a type II error increases when…

A

the sample size is too small

to decrease this risk, a power analysis is performed to determine the sample size needed to detect a true difference between groups

47
Q

____ is the probability that a test will REJECT the null hypothesis correctly / to avoid a type II error

A

power

power = 1-B

48
Q

As the power increases, the chance of a type II error inc or dec?

A

decreases

49
Q

____ is the ratio of risk in the exposed group (treatment) divided by risk in the control group

A

relative risk (RR)

RR= risk in tx group/ risk in control group

50
Q

RR = 1 (or 100%) implies

A

no difference in risk of the outcome between groups

51
Q

RR >1 implies

A

greater risk of the outcome in the treatment group

more risk

52
Q

RR <1 implies

A

lower risk of the outcome in the treatment group

less risk

53
Q

lets say RR=0.57, what does this mean?

A

patients treated with the treatment were 57% AS LIKELY to have progression of disease as placebo-treated patients

57% reduced risk

RR=AS LIKELY

54
Q

lets say RR = 1.5 what does this mean?

A

indicates that there is 50% greater than/increased risk in the treatment group

55
Q

What is calculated after the RR to indicate how much the risk is reduced in the treatment group?

A

relative risk reduction

56
Q

how do you calculate RRR?

A

(%risk in control group - %risk in treatment group)/ (%risk in control group)

OR

1-RR

57
Q

lets say the RRR is 43% what does this mean?

A

treatment group are 43% LESS LIKELY to have HF progression than placebo treated

RRR=LESS LIKELY

58
Q

_____ is more useful than RR and RRR because it includes the reduction in risk AND the incidence rate of the outcome

A

absolute risk reduction

59
Q

ARR calculation

A

(% risk in control group - % risk in treatment group) = ARR

60
Q

lets say the ARR is 12% what does this mean?

A

12 out of 100 patients benefit from the treatment

61
Q

____ is the number of patient who need to be treated for a certain period of time in order for ONE patient to benefit

A

NNT

*rounded UP

62
Q

NNT =

A

1/ARR

63
Q

Lets say NNT =9, what does this mean?

A

for every 9 patients who receive treatment for one year, HF progression is prevented in one patient

64
Q

____ is the number of patients who need to be treated for a certain period of time in order for ONE patient to experience harm

A

NNH

*rounded DOWN

65
Q

NNH=90 what does this mean?

A

one additional case of major bleeding is expected to occur for every 90 patients taking clopidogrel instead of placebo

66
Q

Which studies are not suitable for relative risk calculations?

A

case control studies – odds ratio!

67
Q

In order to estimate the risks associated with a treatment or some type of intervention in a CASE CONTROL study, ___ is caclulated instead

A

odds ratio

68
Q

Odds ratio can be used in what studies

A

most commonly case control

but also cohort and cross sectional

69
Q

OR =

A

AD/BC

A- # that have the outcome, with exposure
B- # without the outcome, with exposure
C- # that have the outcome, without exposure
D- # without the outcome, without the exposure
*prob set up the chart pg 220

70
Q

OR= 1.23 what does this mean?

A

treatment is associated with a 23% INCREASED risk of falls with fractures

71
Q

When do you use hazard ratio instead?

A

in a survival analysis, analysis of death or disease progression

rate at which an unfavorable event occurs within a SHORT period of time

72
Q

HR =

A

HR in treatment group/ HR in control group

*use primary endpoint

73
Q

HR =1 what does this mean

A

there is no benefit to CVD risk when adding treatment to therapy

74
Q

OR or HR = 1

A

the event rate is the same, no advantage of treatment

75
Q

OR or HR >1

A

the event rate in the treatment group is HIGHER

HR of 2 = for an outcome of death, indicates that there are twice as many deaths in the treatment group

76
Q

OR or HR <1

A

the event rate in the treatment group is LOWER

77
Q

______ combines multiple individual endpoints into one measurement

A

composite endpoint

78
Q

For continuous data that is normally distributed _____ methods are appropriate for the statistical test

A

parametric

if not normally distributed =nonparamteric

79
Q

This is a parametric method used when the endpoint has continuous data and the data is normally distributed.

A

T-test

80
Q

When the data from a single sample group is compared with known data from the general population what test is performed

A

ONE SAMPLE T-test

81
Q

if a single sample group is used for a pre- or post- measurement (ex: the patient serves as their own control) what test is appropriated

A

paired t-test

82
Q

this test is used when the study has TWO independent samples

the treatment and the control groups

for example: a study comparing the reduction in A1C values between metformin and placebo would use this

A

student t-test

83
Q

this test is used to test for statistical signficance when using continuous data with THREE or more samples or groups

A

ANOVA/ f test

84
Q

Types of statistical tests for continuous data

A

t tests

ANOVA

85
Q

What tests are used for discrete (categorical) data aka nominal or ordinal data?

A

chi-square test or fisher’s exact

ex: if a study assesses the difference between two groups in mortality (nominal data) or pain scores based on pain scale (ordinal data) –> chi square test

86
Q

One group numerical/continuous data, parametric test

A

one-sample T test

87
Q

one group has before and after measures, parametric test, numerical/continuous data

A

dependent/paired t -test

88
Q

two groups (treatment and control groups) for numerical continuous data, parametric test

A

independent/unpaired student t test

89
Q

measurements of dose and time are both _____ data

A

continuous

90
Q

________ is a statistical technique that is used to determine if one variable (such as days hospitalized) changes, or is related to another variable (such as incidence of hospital acquired infection)

A

correlation

91
Q

correlation does/does not prove a causal relationship

A

does not

92
Q

________ is used to describe the relationship between a dependent variable and one or more independent variables or how much the value of the dependent variable changes when the independent variable changes

A

regression

linear = continuous data
logistic = categorical data
cox = categorical in a survival analysis
93
Q

Sensitivity is the true

A

positive

describe how effectively a test identifies patients WITH the condition

94
Q

specificity is the true

A

negative

city = negative
describe how effectively a test identifies patients WITHOUT the condition

95
Q

Sensitivity =

A

A/A+C x 100

of people true positive/#total people that tested positive

96
Q

specificity =

A 
D/B+D x 100
#of people true negative/#total people that tested negative
97
Q

sensitivity of 28% means

A

only 28% of patients with the condition will have a positive result
the test is negative in 72% of people with the disease (missed diagnosis)

98
Q

specificity of 87% means

A

the test is negative in 87% of patients without the disease, but 13% of patients without the disease can test positive (incorrect diagnosis)

99
Q

________ analysis includes data for ALL patients originally allocated to each treatment group (active and control) even IF the patient did NOT complete the trial according to study protocol

A

Intention to treat

100
Q

______ analysis is conducted for the subset of the population that did complete according to protocol

A

per protocol

101
Q

These types of trials attempt to demonstrate that the new treatment has roughly the SAME effect as the old treatment

A

equivalence

102
Q

these trials attempt to demonstrate that the new treatment is no worse than the current standard based on the delta margin

A

non-inferiority

delta = the minimal difference in effect between the two groups that is considered clinically acceptable based on previous research

NAPLEX 21 (60 decks)

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