Flashcards in Lecture 6 (causation, variation, stat sig) Deck (20):

1

## Types of asso

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-Noncausal asso (flaw --> bias)

-Noncausal asso (confounding)

-Random asso (random variation)

-Causal asso

2

## Internal validity

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-Assessing design, execution, analysis

-Was it done right or was asso due to bias/confounding/random var?

3

## External validity

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-Generalizability

-Reqs internal validity

-Externally valid if asso = result of basic human physiology

4

## Types of causes (2, not combos)

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-Necessary: must precede, w/o which doesn't develop

-Sufficient: leads to disease, but w/o which disease could develop due to smtg else

5

## Types of causes (combos)

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-Necessary and sufficient: very rare

-Necessary but not sufficient: all req'd

-Sufficient but not necessary: exposure alone causes, but so do others

-Neither: most chronic diseases

6

## Criteria for causality

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-Temporal relationship

-Strength of asso

-Dose-response

-Replication of findings

-Biologic plausibility

-Consider alternate explanations

-Cessation of exposure

-Specificity of disease

-Consistency w/other knowledge

7

## Inarguable criteria for causality

### -Temporal relationship: exposure must precede onset of disease

8

## Strength of asso: what does it means for causality

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-Stronger asso less likely to be explained by confounding

-But weak assos can be causal, strong assos can be non-causal

9

## Overall assessment of asso btwn alc + breast cancer

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-Temporality: yes

-Strength: weak (<2)

-Dose-response: yes

-Replication: yes (many not stat sig though)

-Biologic plausibility: some

-Alt explanations considered: yes

-Cessation: no ev

-Specificity: no

10

## Point estimate

### -Estimate of the asso a study is measuring

11

## Test of stat sig

### -Prob that an asso occurred due to random variation

12

## P value (def and what it means when not sig)

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-Prob that asso at least as large as that observed could occur by chance

-When it's not sig: doesn't mean it was due to random chance, ev just not strong enough to reject/accept Ho

13

## Sig level

### -Prob that a sig asso will occur when there really is none

14

## Type I error

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-Rejectct Ho when it's really true

-Saying asso exists when it really doesn't

=alpha

15

## Confidence Interval (def and benefits)

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-Interval that, w/given prob, contains true value

-Provide more info than p-value

16

## Power (def and formula)

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-Prob that study will demonstrate an asso if it truly exists

=1-beta

17

## Beta

### -Prob that a true asso will not be observed

18

## Type II error

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-Failing to reject false Ho

-Saying asso doesn't exist when it really does

19

## What determines power

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-Incidence (cohort): max when 1/2 develop

-Prev of exposure (case-control): max when 1/2 exposed

-Strength of true asso

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