In: Statistics and Probability
What is meant by “bias due to selective survival” in cross-sectional studies? (In your answer, make sure to define appropriate selection probability parameters.) Under what circumstances might there be no selective survival bias even if the selection probabilities are not all equal? Suppose that you could assess that the direction of possible selective survival bias in your study was towards the null. If your study data yielded a non-statistically significant odds ratio of 1.04, would it be correct to conclude that there was no exposure-disease association in your source population? Explain
2.Stats and Probability
What is meant by "bias due to selective survival" in cross-sectional studies? (In your answer, make sure to define appropriate selection probability parameters.)
Only survivors can be included in cross-sectional studies. If exposed cases are more likely to survive longer than unexposed cases or vice versa. the conclusions obtained from a cross-sectional study might be different form an appropriate cohort study; if so there is bias due to selective survival.
Under what circumstances might there be no selective survival bias even if the selection probabilities are not all equal?
There may be no selective survival bias if the cross product of selection probabilities equals 1, even if the selection probabilities are not all equal.
Suppose that you could assess that the direction of possible selective survival bias in your study was towards the null. If your study data yielded a non-statistically significant odds ratio of 1.04, would it be correct to conclude that there was no exposure-disease association in your source population? Explain.
If the bias was towards the null, then the true odds ratio would be larger than 1.04, and therefor possibly large as well as statistically different for the null value. Therefore, it would not be correct to conclude that there was no exposure disease association in the source population.
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