statistics Flashcards

1
Q

Sensitivity

A

TP/(TP+FN)

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2
Q

Specificity

A

TN/(TN+FP)

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3
Q

PPV

A

TP/(FP+TP)

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4
Q

NPV

A

TN/(FN+TN)

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5
Q

Positive Likelihood ratio

A

LR+ = Sn/(1-Sp)

Likelihood that positive test expected in patient with disease compared with positive test result in patient without the disease

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6
Q

Negative Likelihood ratio

A

LR- = (1-Sn)/Sp

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7
Q

Pretest Odds

A

pretest odds= pretest prob/(1-pretest prob)

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8
Q

Post test odds

A

post test odds = pretest odds x LR

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9
Q

Post test probablility

A

Post test prob = post test odds/(1+post test odds)

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10
Q

Absolute risk AKA Event rate

A

events in group/total patients in group

Often calculated for experimental event rate EER and controlled event rate CER

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11
Q

Relative risk

A

RR= EER/CER

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12
Q

Absolute risk reduction

A

ARR= EER-CER

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13
Q

Relative risk reduction

A

RRR= (EER-CER)/CER

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14
Q

NNT

A

NNT= 1/ARR

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15
Q

NNH

A

NNH= 1/ARI where ARI is absolute risk increase which is EER-CER where the outcome is unfavourable

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16
Q

variance

A

variance = SD squared

17
Q

standard error of the mean

A

SD/(square root n)

18
Q

Small sample size increases the chance of what type of error with respect to the null hypothesis

A

Type II error

19
Q

Type 1 error

A

incorrect rejection of the true null hypothesis

20
Q

Type II error

A

Incorrect rejection of the false null hypothesis

21
Q

hazard ratio

A

Sort of like relative risk. Used in survival analysis to reflect time survived to an event. useful if risk not constant with respect to time

22
Q

Cohort study

A

prospective
cohort + exposure –>?disease
cohort + no exposure–>?disease

23
Q

Case control

A

Retrospective
Disease–>?exposed
Control without disease –>?exposed

24
Q

Phase 1 trial

A

pharmacokinetics

25
Q

Phase II trial

A

Safety

26
Q

Phase III trial

A

Efficacy

27
Q

Phase IV trial

A

Long term safety
Real life application
Different patient groups from earlier trials

28
Q

When is the chi-squared test used?

A

Used to compare proportions or percentages.