Lecture 5 - Statistical (Bayesian) Inference
Exam Questions With Correct Answers.
What is the wrong question frequentist approach asks? - answer-provides answers to what is
often the wrong question P(data | H0)
-really want P(HA | data)
sensitivity - answerP(T+|D+)
PPV - answerP(D+|T+)
diagn...
What is the wrong question frequentist approach asks? - answer✔✔-provides answers to what is
often the wrong question P(data | H0)
-really want P(HA | data)
sensitivity - answer✔✔P(T+|D+)
PPV - answer✔✔P(D+|T+)
diagnostic test -> research study
absence of disease - answer✔✔truth of null hypothesis
diagnostic test -> research study
presence of disease - answer✔✔truth of alternative hypothesis
diagnostic test -> research study
positive result (test outside normals) - answer✔✔positive result (reject null)
diagnostic test -> research study
negative result (within normals) - answer✔✔negative result (fail to reject null)
diagnostic test -> research study
sensitivity - answer✔✔power
diagnostic test -> research study
FP (1 - specificity) - answer✔✔significance level (alpha)
diagnostic test -> research study
prior Pr(disease) - answer✔✔prior Pr(hypothesis)
diagnostic test -> research study
predictive value of a +ve test - answer✔✔predictive value of a +ve study
what does the Pr(positive finding) depend on? - answer✔✔-prior probability
-statistical power
-significance level
-bias (if present)
R - answer✔✔odds of a true relationship
Pr(R) = R / (R+1) - answer✔✔standard formula converting odds to probability
= odds of a true relationship / (odds of a true relationship + 1)
Pr (not R) = - answer✔✔1 / (R + 1)
c - answer✔✔# of relathionships
The smaller the studies conducted in a scientific field, the less likely the research findings are to
be true - answer✔✔-since decreased power (1-B) means PPV gets smaller so findings are:
--less likely to be true in small studies
--more likely to be true in large RCTs
The smaller the effect sizes in a scientific field, the less likely the research findings are to be true
- answer✔✔-power depends also on effect size so research findings
effect size - answer✔✔-a simple way of quantifying the difference between two groups that has
many advantages over the use of tests of statistical significance alone
-emphasizes the size of the difference rather than confounding this with sample size.
the greater the number and the lesser the selection of tested relationships in a scientific field, the
less likely the research findings are to be true - answer✔✔-post study results depend on your
prior beliefs
-increased probability in large phase III confirmatory studies
the greater the flexibility in designs, definitions, outcomes, and analytical modes in a scientific
field, the less likely the research findings are to be true - answer✔✔question of bias, selective
reporting
the greater financial interest and prejudice, the less likely the research findings are to be true -
answer✔✔question of bias
the hotter the scientific field (w more teams involved), the less likely the research findings are to
be true - answer✔✔proteus phenomenon of alternating extreme research claims
u - answer✔✔bias
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