Stats/Ethics Flashcards

1
Q

What variables to use mean for

A
  • Interval (ordered, numerical, where zero means nothing)
  • Ratio (ordered, numerical, where zero means something)
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2
Q

What variables to use median for

A
  • Ordinal (ordered, named categories)
  • Non-normally distributed interval/ratio
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3
Q

What variables to use mode for

A
  • Nominal (named categories like gender)
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4
Q

Normal distribution has what percentage with 1 SD vs 2 SD

A

68% with mean +/- 1 SD
95% with mean +/- 2 SD

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5
Q

Calculation for standard error of mean

A

= Sample standard deviation / sq root of sample size

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6
Q

Relative risk calculation

A
  • Chance of getting disease with treatment relative to placebo
    (Treated with disease / all treated) / (Placebo with disease / all placebo)
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7
Q

Odds ratio calculation

A
  • Number of disease in treated / number of diseased in placebo
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8
Q

Number needed to treat calculation

A

1 / risk difference

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9
Q

Absolute risk reduction

A

Difference in risk between treatment and placebo
= (Diseased placebo / all placebo) / (Diseased treated / all treated)

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10
Q

Sensitivity calculation

A

Given a patient with disease, what’s the chance the test will be positive

  • True + / All with disease
  • SnOUT - 100% sensitive rules OUT disease
  • Good screening tests have high sensitivity
  • Higher sensitivity means higher false positive
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11
Q

Specificity calculation

A

Given a healthy patient, what’s the chance test will be negative

  • True - / All healthy
  • SpIN - 100% specific rules IN disease
  • Higher specificity is higher false negative
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12
Q

Positive predictive value calculation

A

True + / All + test

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13
Q

Negative predictive value calculation

A

True - / All - test

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14
Q

Likelihood ratio calculations

A

Chance of a positive (or negative) test result in patient with disease relative to patient without disease

LR + = (True pos / all disease) / (False positive / all healthy)

LR - = (False neg / all disease) / (True neg / all healthy)

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15
Q

Receiver operating curve graph ideal test

A

Sensitivity on y axis
1 - specificity on x axis
Best test is in the top left corner

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16
Q

Cohort study design

A

Follow exposed and non-exposed forward in time to see if they get bad outcome
- Good for rare exposures, can measure prevalence of a disease

17
Q

Case control study design

A
  • Collect cases and controls and look back in time to see if they were exposed
  • Good for rare diseases, can’t measure prevalence
18
Q

Which tests to use for means (with 2, before/after and more than 2)

A
  • 2: Student T-tests
  • Before/after: paired T tests
  • More than 2: ANOVA
19
Q

Which tests to use for medians (with 2, before/after)

A
  • 2: Mann-Whitney-U
  • Before/after: Wilcoxon signed
20
Q

Which test to use for time to event

A

Kaplain Meier

21
Q

Which test to use for proportions

A

Chi square
- Fischer’s test for small group

22
Q

Which test to use to predict a number or yes/no

A

Linear regression