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STATISTICS Flashcards

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1
Q

CLINICAL TRIAL PHASES
what is a phase 0 trial?

A
  • exploratory studies
  • involves a small number of participants and aims to assess how a drug behaves in the human body
  • assesses pharmacokinetics and pharmacodynamics
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2
Q

CLINICAL TRIAL PHASES
what is a phase 1 trial?

A
  • safety assessment
  • determines side effects prior to larger studies
  • conducted on healthy volunteers
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3
Q

CLINICAL TRIAL PHASES
what is a phase 2 trial?

A
  • assesses efficacy
  • involves a small number of patients affected by a particular disease
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4
Q

CLINICAL TRIAL PHASES
what are the sub-divisions of phase 2 trials?

A

2a = assesses optimal dosing
2b = assesses efficacy

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5
Q

CLINICAL TRIAL PHASES
what is a phase 3 trial?

A
  • assesses effectiveness
  • typically involves 100-1000s of people
  • often part of randomised control trial
  • comparing new treatment to established treatments
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6
Q

CLINICAL TRIAL PHASES
what is a phase 4 trial?

A
  • post-marketing surveillance
  • monitors for long-term effectiveness and side effects
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7
Q

SIGNIFICANCE TESTS
which tests are parametric (something can be measured)?

A
  • student’s t-test (paired and unpaired)
  • Pearson’s product of moment coefficient (correlation)
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8
Q

SIGNIFICANCE TESTS
what is the difference between the paired and unpaired student’s t-test?

A

paired = data obtained from a single group of patients e.g. measurements before + after intervention

unpaired = data from two different groups of patients e.g. comparing response to different interventions in two groups

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9
Q

SIGNIFICANCE TESTS
which tests are non-parametric?

A
  • Mann-Whitney U test
  • Wilcoxon signed-rank test
  • chi-squared test
  • spearman, kendall rank
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10
Q

SIGNIFICANCE TESTS
what is the Mann-Whitney U test?

A

compares ordinal, interval or ratio scales of unpaired data

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11
Q

SIGNIFICANCE TESTS
what is Wilcoxon signed-rank test?

A

compares two sets of observations on a single sample e,g, a before and after test on the same population following an intervention

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12
Q

SIGNIFICANCE TESTS
what is the chi-squared test?

A

used to compare proportions or percentages e.g. compares the percentages of patients who improved following two different interventions

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13
Q

SIGNIFICANCE TESTS
what is the spearman, kendall rank?

A

correlation

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14
Q

NULL HYPOTHESIS
what is a null hypothesis?

A

H0 = states that two treatments are equally effective
(there is no difference)

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15
Q

NULL HYPOTHESIS
what is the p value?

A
  • is the probability of obtaining a result by chance at least as extreme as the one actually observed, assuming the null hypothesis is true
  • it is equal to the chance of making a type 1 error
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16
Q

NULL HYPOTHESIS
what are the two different types of error that may occur when testing the null hypothesis?

A
  • type 1 = null hypothesis rejected when it is true
  • type 2 = null hypothesis is accepted when it is false
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17
Q

NULL HYPOTHESIS
what is the power of a study?

A
  • it is the probability of (correctly) rejecting the null hypothesis when it is false
  • power = 1 - probability of type 2 error
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18
Q

NULL HYPOTHESIS
what factors influence power?

A
  • sample size
  • meaningful effects size (decided at beginning of study)
  • significance level
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19
Q

NULL HYPOTHESIS
how can the power of a study be increased?

A
  • increase the sample size
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20
Q

BIAS
what is the Hawthorne effect?

A
  • people change their behaviour due to the knowledge that it is being studied
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21
Q

BIAS
what is late-look bias?

A
  • gathering information at an inappropriate time
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22
Q

FOREST PLOTS
what are forest plots used for?

A
  • found in meta-analyses + provide graphical representation of strength of evidence of constituent trials
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23
Q

FOREST PLOTS
what does the large vertical line on a forest plot represent?

A

the line of no effect

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24
Q

FOREST PLOTS
what do the small vertical lines on forest plots represent?

A

the mean

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25
FOREST PLOTS what does the horizontal line on a forest plot represent?
the confidence interval (usually 95%)
26
FUNNEL PLOT what is a funnel plot usually used to demonstrate?
- the existence of publication bias in meta-analyses
27
FUNNEL PLOT what does a symmetrical inverted funnel represent?
- publication bias is unlikely
28
FUNNEL PLOT what does an asymmetrical funnel represent?
indicates relationship between treatment effect and study size
29
GRAPHS what does a box and whisker plot represent?
- sample minimum, lower quartile, median, upper quartile and sample maximum
30
GRAPHS what is a histogram used for?
graphical display of continuous data where values have been categorised into a number of categories
31
GRAPHS what is a scatter plot used for?
graphical representation using Cartesian coordinates to display values for two variables for a set of data
32
GRAPHS what is a Kaplan-Meier survival plot?
a plot of the Kaplan-Meier estimate of survival function showing decreasing survival with time
33
HAZARD RATIO what is it?
similar to relative risk but used when risk is not constant to time used when analysing survival over time
34
RELATIVE RISK what is it?
the ratio of risk in the experimental group to risk in the control group RR = EER/CER EER = experimental event rate CER = control event rate
35
RELATIVE RISK what does is mean if the risk ratio is >1?
the rate of the event is increased compared to controls it is therefore necessary to calculate relative risk increase
36
RELATIVE RISK what does it mean if risk ratio <1?
the rate of the event is decreased compared to controls therefore relative risk reduction should be calculated
37
INCIDENCE what is it?
number of new cases per population in a given time
38
PREVALENCE what is it?
total number of cases per population at a particular point in time
39
PREVALENCE what are the 2 different types of prevalence?
- point prevalence - period prevalence
40
PREVALENCE what is point prevalence?
number of cases in a defined population / number of people in a defined population at the same time
41
PREVALENCE what is period prevalence?
number of identified cases during a specified period of time/total number of people in that population
42
PREVALENCE what is the relationship of prevalence and incidence in chronic diseases?
prevalence is much greater than incidence
43
PREVALENCE what is the relationship of prevalence and incidence for acute diseases?
prevalence and incidence are similar
44
INTENTION TO TREAT ANALYSIS what is it?
analysis of RCTs where all patients randomly assigned to one of the treatments are analysed together, regardless of whether or not they completed or received treatment it is done to avoid effects of crossover or drop-out
45
NORMAL DISTRIBUTION what are the properties?
mean = mode = median
46
NORMAL DISTRIBUTION what percentage of values lie within 1SD of the mean?
68.3%
47
NORMAL DISTRIBUTION what percentage of values lie within 2SD of the mean?
95.4%
48
NORMAL DISTRIBUTION what percentage of values lie within 3SD of the mean?
99.7%
49
NORMAL DISTRIBUTION what percentage of values lie within 1.96SD of the mean?
95%
50
NORMAL DEVIATION what is standard deviation?
a measure of how much dispersion exists from the mean SD = square root of variance
51
NORMAL DISTRIBUTION what is variance?
it is the measure of spread of scores away from the mean variance = square of SD
52
NUMBER NEEDED TO TREAT how do you calculate it?
1/ARR ARR = EER - CER EER = experimental event rate (no with outcome/total no with intervention) CER = control event rate (no with outcome in control/total no with control)
53
STUDY DESIGN what is the usual outcome measure in cohort studies?
relative risk
54
STUDY DESIGN what is the usual reported measure in case-control studies?
odds ratio
55
ODDS RATIO how do you calculate odds ratio?
odds ratio = odds of result with intervention / odds of result with control -------------------------------------------------------------------- odds of result with intervention = no with result/no with no result odds of result with control = no with result/no with no result
56
SCREENING TEST STATISTICS what is sensitivity?
proportion of people with the condition who have a positive test result TP / (TP + FN)
57
SCREENING TEST STATISTICS what is specificity?
proportion of people without the condition who have a negative test result TN / (TN + FP)
58
SCREENING TEST STATISTICS what is positive predictive value?
the chance that the patient has the condition if the diagnostic test is positive TP / (TP + FP)
59
SCREENING TEST STATISTICS what is negative predictive value?
the chance that the patient does not have the condition if the diagnostic test is negative TN / (TN + FN)
60
SCREENING TEST STATISTICS what is the likelihood ratio for a positive test result?
how much the odds of the disease increase when a test is positive sensitivity / (1 - specificity)
61
SCREENING TEST STATISTICS what is the likelihood ratio for a negative test result?
how much the odds of the disease decrease when a test is negative? (1 - sensitivity) / specificity
62
SCREENING TEST STATISTICS what is precision?
quantifies a tests ability to produce the same measurements with repeated tests
63
SKEWED DISTRIBUTION what is positively skewed distribution?
mean > median > mode
64
SKEWED DISTRIBUTION what is negatively skewed distribution?
mean < median < mode

MY REVISION - ALL PHASES (36 decks)

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