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PHM > Evidence-Based Medicine > Flashcards

Evidence-Based Medicine Flashcards

0
Q

P value

A

The probability of obtaining the observed result by chance rather than as a result of accrue effect

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1
Q

Alpha level

A

The highest risk of making false positive error that the investigator is willing to accept

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2
Q

Bayes theorem

A

If result is positive, probability that patient has the disease
If result is negative, probability that patient doesn’t have disease

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3
Q

attributable risk percent in there exposed

A

Among those exposed to y, what % of total risk for disease x is attributable to y

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4
Q

Population attributable risk percent

A

Among the population, what % of x is caused by exposure to y

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5
Q

Population attributable risk

A

Among the general population, how much of the total risk of fatal disease x is caused by exposure to y

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6
Q

Risk difference

A

A measure of absolute risk, aka attributable risk…. The risk in there exposed group minus the risk in the unexposed group

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7
Q

Rate difference

A

The rate in the exposed group minus the rate in higher unexposed group

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8
Q

Relative risk = risk ratio

A

The ratio of the risk in the exposed group to the risk in the unexposed group. If rr < or = 1, no association or negative association

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9
Q

Mortality ratio

A

Occurrence mortality in intervention group relative to controls

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10
Q

Strengths and weaknesses of: rct

A

Large numbers of participants
Less bias
Gold standard for testing hypotheses

Unethical to test harmful exposures
Expensive

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11
Q

Strengths and weaknesses of: cohort study

A

Can measure multiple outcomes for any one exposure
Can demonstrate a direction on causality
Can measure incidence and prevalence

Prone to loss of follow up bias
Confounding (non randomised)
Costly and time consuming

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12
Q

Want kind of study measures one outcome and many risk factors?

A

Case control

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13
Q

Want kind of study is susceptible to late look bias

A

Cross sectional

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14
Q

Want kind of study is based on exposure

A

Cohort

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15
Q

Want kind of study is based on known cases

A

Case control

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16
Q

What study is really good for rare diseases

A

Case control

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17
Q

Ecological fallacy

A

Inferences drawn to individuals based on populations

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18
Q

Want kind of study is good for interesting/new/unusual cases

A

Case series

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19
Q

What studies can test a hypothesis

A

Rct ( gold standard) or case control or cohort or ecological

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20
Q

Which is stronger and why: prospective or retrospective cohort

A

Prospective, due to the ability to monitor and control data collection

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21
Q

Provide and example of stratified allocation

A

Even spread across different blocks

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22
Q

What is the goal of case control studies

A

To determine differences in risk factors in participants with a particular outcome and participants without the outcome

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23
Q

A t-test measures how ______ the _________ is between two ______

A

Big the difference is between two means

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24
Q

A t-test takes into account the:

A

Variability between score and distributions

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25
Q

A 95% confidence interval asserts that

A

If there experiment were replicated 100 times, 95 of those times would contain the population parameter

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26
Q

Unlike probability values, confidence intervals provide information about the _____ of an estimate

A

Precision :)

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27
Q

The standard error is

A

A measure of precision of a SAMPLE statistic

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28
Q

A standard deviation is

A

A measure of precision of the POPULATION DISTRUBTION

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29
Q

Which hypothesis would you reject if t< critical value?

A

Alternative

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30
Q

Which hypothesis would you accept if t< critical value?

A

Null hypothesis

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31
Q

What is the critical level?

A

A number found in a table that you compare the t-test too to determine significance.

32
Q

You want t to be _____ critical value for significant findings

A

Greater than

33
Q

In a false positive error, you incorrectly accept the _____ hypothesis

A

Alternative

34
Q

When the data represents pre-trial and post-trial results for a single group of subjects, use a _________ t test

A

Paired

35
Q

What does a negative t score indicate?

A

That pretrial values were greater than post trial values…ie there has been a reduction

36
Q

Risk difference

A

The proportion of the risk in the exposed that is due to or attributable to the exposure

37
Q

A harmful exposure will yield a _______ greater than 1

A

Risk difference

38
Q

Odds ratios are useful in ______ study designs

A

Case control

39
Q

Bayes is used in medicine in:

A 
Analysis of clinical decisions in
Community screening program
Individual patient care
By
Calculating ppv and posterior probabilities
40
Q

In bayes theorem the numerator represents

A

True positive results

41
Q

When applying bayes theorem to the care of an individual patient, try prior probability is analogous to….

A

Prevalence

42
Q

To apply bayes theorem to a screening program which 3 bits of information should be known

A

Prevalence, specificity and sensitivity

43
Q

As an equation, Probability =

A

Number of favourable outcomes/

Number of possible equally likely outcomes

44
Q

In a normal distribution ___% fall either side 1SD, and ___% 2SD

A

68 and 95

45
Q

Alpha can/cannot be used as the basis for ejecting the nul hypothesis

A

Can

46
Q

Inductive reasoning

A

Specific to general

Generalising

47
Q

Deductive reasoning

A

General to specific

Deducing

48
Q

Binomial probability distribution

A

Used to describe variables with two levels

49
Q

What is the advantage of an observational experimental design?

A

Can be used where it is unethical to withhold a treatment

50
Q

What does a correlational study design measure?

A

Association, not causation

51
Q

Nominal and ordinal are__________.

We use _________ correlation for ORDINAL data.

A

Non parametric

Spearman’s

52
Q

Nominal data

A

Categories that have no relationship to each other e.g. Blood type

53
Q

Ordinal data

A

Categories that have a relationship e.g. Young middle-aged and old

54
Q

Interval and ratio data are_____. We use _________ correlation

A

Parametric types of data.

Pearson’s

55
Q

Interval data

A

Related but no absolute zero e.g. Iq

56
Q

Ratio data

A

Parametric data with absolute zero e.g. Blood pressure

57
Q

Chi square test is a measure of________ that allows us to calculate ________

A

Difference, not association

Statistical significance

58
Q

Define correlation

A

A measure of association between variables

59
Q

When do you use a student’s t-test?

A

When there are two separate groups of participants

60
Q

What is the difference between t tests and z tests?

A

T tests measure differences in means

Z tests measure differences in proportions

61
Q

Critical ratio

A

Uses t or z test to a calculate a ratio between a parameter and the SE of that parameter

62
Q

The nul hypothesis for a chi squared test of a 2x2 contingency table is that:

A

The two variables are independent of each other (variation in one variable is not caused in part but variation in another variable)

63
Q

What category does an interventional study design fall under?
Strength and weakness?

A

Experimental
S: reduce ill health in entire community, increase health literacy, behaviours and environment
W: limited randomisation and difficulty in follow up

64
Q

What are the phases of drug development/ public health intervention?

A 
Basic science   (discovery/1)
M ethod development  (1/2)
E fficacy  (2/3)
E ffectiveness  (3/4)
D issemination  (4/5)
65
Q

Strengths and weaknesses of case control

A

S: less expensive than cohort, good for rare, multiple exposures

W: selection, recall and observer bias, only a single outcome, temporal relationships difficult to decipher

66
Q

MR < 1 indicates that there is ______ mortality in the intervention group

A

Decreased

67
Q

If an attributable risk is <0, factor investigated is protective or harmful?.

A

Protective

68
Q

Degrees of freedom

A

N-1 in students

N-2 in paired

69
Q

How do 1 way and 2 way anova differ?

A

Number of independent variables being tested

70
Q

What kind of data do you use anova on?

A

Dependent is continuous

Independent is categorical

71
Q

5as

A 
Ask
Access
Appraise
Apply
Audit
72
Q

Picot

A

People
Intervention
Comparison control
Outcome

73
Q

Why can’t we calculate incidence in a case control study ?

A

The study population has been selected on the basis of hype heir disease

74
Q

Attributable risk

A

Ar = risk(ex) - risk(unex)

75
Q

Relative risk equation

A

Risk(ex) / risk(unex)

76
Q

OR

A

Ad/bc

77
Q

Ar(%)

A

= [risk(ex) - risk(unex)] / risk(unex) (x100)

PHM (3 decks)

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