Lecture 6 (causation, variation, stat sig) Flashcards Preview

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Flashcards in Lecture 6 (causation, variation, stat sig) Deck (20):
1

Types of asso

-Noncausal asso (flaw --> bias)
-Noncausal asso (confounding)
-Random asso (random variation)
-Causal asso

2

Internal validity

-Assessing design, execution, analysis
-Was it done right or was asso due to bias/confounding/random var?

3

External validity

-Generalizability
-Reqs internal validity
-Externally valid if asso = result of basic human physiology

4

Types of causes (2, not combos)

-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)

-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

-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

-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

-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)

-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

-Rejectct Ho when it's really true
-Saying asso exists when it really doesn't
=alpha

15

Confidence Interval (def and benefits)

-Interval that, w/given prob, contains true value
-Provide more info than p-value

16

Power (def and formula)

-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

-Failing to reject false Ho
-Saying asso doesn't exist when it really does

19

What determines power

-Incidence (cohort): max when 1/2 develop
-Prev of exposure (case-control): max when 1/2 exposed
-Strength of true asso

20

alpha

-Give % of assos expected to be sig due to chance alone (when studying multiple)