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1
Q

Define specificity

A

Proportion of patients without the condition who have a negative result

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2
Q

Formula for specificity

A

TN / TN + FP

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3
Q

Define sensitivity

A

Proportion of patients with the condition who have a positive test result

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4
Q

Formula for sensitivity

A

TP / TP + FN

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5
Q

Define positive predictive value

A

The chance that the patient has the condition if the diagnostic test is positive

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6
Q

Formula for positive predictive value

A

TP / TP + FP

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7
Q

Define negative predictive value

A

The chance that the patient does not have the condition if the diagnostic test is negative

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8
Q

Formula for negative predictive value

A

TN / TN + FN

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9
Q

Define likelihood ratio for a positive test result

A

How much the odds of the disease increase when a test is positive

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10
Q

Formula for likelihood ratio for a positive test result

A

sensitivity
/
(1 - specificity)

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11
Q

Define likelihood ratio for a negative test result

A

How much the odds of the disease decrease when the test is negative

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12
Q

Formula for the likelihood ratio for a negative test result

A

(1 - sensitivity)
/
specificity

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13
Q

Which significance tests are used on parametric data?

A

Student’s t- test (paired or unpaired)

Pearson’s product-moment coefficent (for correlation)

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14
Q

Which significance test is used on non-parametric data for comparing ordinal, interval or ratio scales of unpaired data?

A

Mann-Whitney U test

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15
Q

Which significance test is used on non-parametric data comparing two sets of observations on the same sample (e.g. before and after)

A

Wilcoxon signed-rank test

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16
Q

Which significance test is used to compare proportions or percentages on non-parametric data?

A

Chi-squared test

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17
Q

Which significance test is used for measuring correlation in non-parametric data?

A

Spearman, Kendall rank

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18
Q

Relationship between mean, median and mode in normal distributed data

A

mean = median = mode

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19
Q

Relationship between mean, median and mode in positively skewed data

A

mean > median > mode

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20
Q

Relationship between mean, median and mode in negatively skewed data

A

mean < median < mode

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21
Q

What is the goal of a phase 1 trial?

A

Determine pharmacokinetics and pharmacodynamics and side effects

Small study on healthy volunteers

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22
Q

What is the goal of a phase 2 trial?

Goals of 2a and 2b trials

How many patients?

A

Assess dosage and efficacy

2a = dosage
2b = efficacy

Small number of patients affected by disease

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23
Q

What is the goal of phase 3 trial?

A

Assess effectiveness

Large RCT comparing new treatment to old

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24
Q

What is the goal of a phase 4 trial?

A

Monitoring long term effectiveness and side effects

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25
Formula for numbers needed to treat
1 / (absolute risk reduction)
26
How to calculate the absolute risk reduction
Control event rate - experimental event rate
27
How to calculate the control event rate
number who had outcome with control / total number who had the control
28
How to calculate the experimental event rate
number who had outcome with the intervention / total number who had the intervention
29
What is the usual outcome measure for a cohort study?
Relative risk
30
What is the usual outcome measure for a case-control study?
Odds ratio
31
What does endemic mean?
Persistent, usual or expected level of disease in a given population
32
How to calculate the relative risk
EER / CER
33
How to calculate the relative risk reduction or relative risk increase
EER - CER / CER
34
What is a type 1 error?
The null hypothesis is rejected when it is true
35
What is a type 2 error?
The null hypothesis is accepted when it is false
36
What is the name given to a phenomenon where if a variable is extreme on its first measurement, it will tend to be closer to the average on its second measurement
Regression
37
What statistical test to use on data with several groups?
ANOVA
38
What is ANOVA used for?
Comparing the variance of the means Several groups of data Normally distributed data
39
What is a spurious association?
Arisen by chance and not real
40
What is an indirect association?
Association is due to another factor (a confounding variable)
41
What is a direct association?
True association not linked by a third variable
42
What criteria are use to establish causation?
Bradford Hill Causal Criteria
43
How to calculate standard deviation
√variance
44
How to calculate standard error of the mean
standard deviation / √n
45
What is confounding?
A variable that correlates to other variables within a study, leading to spurious results
46
How can you control confounding at the design stage of an experiment?
Randomisation
47
How can you control confounding at the analysis stage of an experiment?
Stratification
48
What is nominal data?
Values put into categories with no order e.g. birth place
49
What is ordinal data?
Values put into categories which can be ordered e.g. NYHA classification of heart failure
50
What is discrete data?
Values confined to certain values e.g. number of asthma exacerbations per year
51
What is continuous data?
Data can take any value within a certain rage e.g. weight
52
What is binomial data?
Data may take one of two values e.g. gender
53
What is the delphi method?
Method of asking for then collating expert opinion
54
Issues with the delphi method
Time consuming Low response rates Investigators can mould responses Expertise of the panelists could be unevenly distributed
55
What is the hierarchy of medical evidence?
1) Metanalysis of RCT 2) 1x RCT 3) Systematic reviews of cohort studies 4) Cohort studies 5) Systematic reviews of case-control studies 6) Case-control studies 7) Case series 8) Expert opinion
56
When is hazard ratio used?
When analysing survival over time
57
What is used to measure general practice workload?
Jarman Underprivileged Area Score
58
What % of values lie within 1 SD of the mean?
68.3%
59
What % of values lie within 2 SD of the mean?
95.4%
60
What % of values lie within 3 SD of the mean?
99.7%
61
What % of values lie within 1.96 SD of the mean?
95%
62
What is the power of a study?
Probability of correctly rejecting the null hypothesis when it is false
63
How is power calculated?
1 - probability of a type 2 error
64
What is the p value?
the probability of obtaining a result by chance as least as extreme as the one that was observed, assuming the null hypothesis was true
65
What does reliability assess?
Consistency
66
What does validity assess?
Accuracy
67
What error is the p value equal to?
Type 1 error
68
Equivalence trial
Equivalence margin of -delt to +delta If CI lies within equivalence margin then drugs have similar effect
69
What are independent variables?
Something that is purposefully changed by the researcher
70
What are dependent variables?
The one that is observed and changes in response to the independent variable
71
What are controlled variables?
All other variables that are not the dependent variable or the independent variable Do not change throughout the study
72
What is the population attributable risk?
Reduction in incidence if the population were entirely unexposed
73
What is the attributable proportion?
Proportion of the disease that would be eliminated if the disease rate were reduced to that of the unexposed group
74
What is a case control study?
Retrospective Participants with condition are identified and matched with control Information then collected on past exposure to a possible causal agent
75
What is a cohort study?
Prospective | Participants selected on their exposure to a particular agent and followed up to see how many develop disease
76
Cross-sectional study
'snap shot' to find prevalence
77
What is the standardised mortality rate?
Observed deaths / expected deaths
78
What does standardised mortality rate of 100 indicate?
Mortality in the group being studied is the same as the standard population
79
What is the mortality rate?
Number of deaths in a particular population at a particular time
80
What is the maternal mortality rate?
deaths linked to childbearing per live births per year
81
What is the infant mortality rate?
Deaths <1 year per live births per year
82
What is the fetal mortality rate?
Fetal deaths per live births per year
83
What is external validity?
Degree to which the conclusions in the study would hold for other persons in other places at other times e.g. ability to generalise
84
What is internal validity?
How confident we are that the change in the independent variable caused the observed change in the dependent variable
85
What is face validity?
Does it appear to test what it is meant to?
86
What is content validity?
Extent to which a test or measure assesses the full content of a subject or area
87
Methods of assessing validity in qualitative research
Triangulation Respondant validation Bracketing Reflexivity
88
What is triangulation in qualitative research?
Compares results from 2 or more different methods of data collection, or from 2 or more data sources Used to assess validity
89
What is respondant validation in qualitative research?
Investigators account is compared to those of research subjects Used to assess validity
90
What is bracketing in qualitative research?
Putting asides ones own beliefs / knowledge
91
What is reflexivity in qualitative research?
Being sensitive to the ways the researcher and research process have shaped the collected data
92
What is work up bias?
Clinicians reluctant to order gold standard test if new test is negaive
93
What is expectation bias?
Observers subconsciously measure/ report data in a way that favours study outcome
94
What is the Hawthorne effect?
group changes its behaviour because it is being watched
95
What is procedure bias?
Subjects in different groups receive different treatments
96
What is anchoring bias?
When the first piece of information influences decisions too much
97
what is late-look bias?
Gathering information at an inappropriate time
98
What is lead time bias?
New test diagnoses earlier but there is no effect on the outcome of the disease
99
What is Berkinson's/hospital bis?
Occurs in case control studies where hospitalised patients are used as controls
100
How to calculate risk
number of events / number at risk
101
how to calculate odds
number of events / number of non-events
102
How to calculate relative risk (or risk ratio)
Risk in exposed group / risk in unexposed group
103
How to calculate odds ratio
Odds of having been exposed / Odds in a control group
104
What does correlation tell us?
How one variable may increase or decrease as another variable changes, but not by how much
105
What does linear regression tell us?
How much one variable changes when a second variable is changed
106
What is cost-effectiveness analysis?
Compares interventions by relating costs to a single clinical measure combines costs and effects into an incremental cost-effectiveness ratio (ICER)
107
What is cost-benefit analysis?
All costs and benefits are measured in terms of money
108
What is cost-utility analysis?
Form of cost-effectiveness analysis but allows comparison between different diseases Uses QALY
109
What method of analysis uses QALY?
Cost-utility analysis
110
What does 1 QALY equal?
1 year in perfect health
111
What does QALY measure?
Gains in life expectancy and health related quality of life can be negative
112
What is cost-minimisation analysis?
Aim is to decide the least costly way of achieving the same outcome

AKT (20 decks)

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