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POPH192 2024 > Module Five > Flashcards

Module Five Flashcards

1
Q

Three components of internal validity?

A

Chance, bias, confounding

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2
Q

Components of chance to identify?

A

95% confidence interval (sample size), Null value, Clinical vs Statistical significance

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3
Q

What does increasing the sample size do?

A

Reduces sampling variability, increases likelihood of getting a representative table and increases precision of parameter estimate

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4
Q

What do you do if the p-value is below 0.05?

A

Reject the null

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5
Q

How do you interpret a confidence interval?

A

x times as likely… we are 95% confident that… and since p-value is less than 0.05 the association is statistically significant, we reject null, unlikely due to chance…

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6
Q

What is a type 1 error?

A

Rejects a null hypothesis that is actually true

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7
Q

What is a type 2 error?

A

Failing to reject the null hypothesis when it’s actually false

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8
Q

If a CI includes the null?

A

p-value > 0.05, fail to reject null, findings not statistically significant

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9
Q

If a CI does not include the null?

A

p-value < 0.05, reject null, findings statistically significant

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10
Q

What are p-values problemtatic?

A

Arbitrary threshold, only about Ho, nothing about importance

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11
Q

What is bias?

A

Any systematic error in an epidemiological study that results in an incorrect estimate of the association between exposure and risk of disease

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12
Q

Three types of bias?

A

Selection bias, Information bias, Publication bias

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13
Q

What can bias cause?

A

Precision parameter being bias towards or away from the null, causing an over/under estimation

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14
Q

When can selection and information bias be controled?

A

Only in design phase

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15
Q

When can publication bias be controled?

A

Only in analysis phase

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16
Q

How do you minimise loss to follow up?

A

Alternative contact, regular contact and several attempts at contact

17
Q

How can you minimise recall bias

A

Objective measures, validate self-reported measures with other information, memory aids

18
Q

How can you minimise interviewer/observer bias?

A

Clearly define study protocol and measures, structure questionnaire and standard prompts, training of interviewers, blinding

19
Q

What are the requirements for something to be a confounder?

A

Independently associated with exposure, Independently associated with outcome, not on the causal pathway

20
Q

What is an overestimation?

A

RR is further from null

21
Q

What is an underestimation?

A

RR is closer to null

22
Q

How can you control for a confounder in the design stage?

A

Randomisation, Matching, Restriction (to a strata)

23
Q

How can you control for a confounder in the analysis stage?

A

Stratification, Multivariable analysis, Age standardisation

24
Q

What are the pros of stratification?

A

Easy for a small number of potential confounders with limited strata, can evaluate impact of confounding, can identify effect modification

25
Q

What are the cons of stratificaition?

A

Can leave residual confounding, not feasible when dealing with lots of potential confounders with many strata

26
Q

What are the cons of multivariable analysis?

A

Can leave residual confounding, not feasible when dealing with lots of potential confounders with many strata, can only control what you’ve measured

27
Q

When is something a counfounder?

A

When it adjusts the measure of association by more than 10%

28
Q

What is effect modification?

A

The effect of exposures and outcomes varies between strata

29
Q

What is a sufficient cause?

A

Combination of component causes that cause disease

30
Q

What does the B in BESTCDS stand for?

A

Biological plausibility - Is there a plausible mechanism for the association?

31
Q

What does the E in BESTCDS stand for?

A

Experimental evidence - Is it an RCT?

32
Q

What does the S in BESTCDS stand for? (1st S)

A

Specificity - is the exposure specifically associated with a particular outcome and not others?

33
Q

What does the T in BESTCDS stand for?

A

Temporal sequencing - which came first, exposure or outcome?

34
Q

What does the C in BESTCDS stand for?

A

Consistency - is study consistent with other studies?

35
Q

What does the D in BESTCDS stand for?

A

Dose-response relationship - does increasing dose cause worse outcome?

36
Q

What does the S in BESTCDS stand for? (2nd S)

A

Strength of association - stronger association means less likely caused by chance

POPH192 2024 (8 decks)

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