Detect which type of bias

[K06100]

An investigator wishes to assess whether vaccination increases the incidence of developmental diseases such as autism. He asks parents of recently diagnosed cases about their child’s vaccination history and compares their responses to those of parents of children who have not been diagnosed with autism. What is the most significant type of potential bias present in this study design?

(A) Confounding bias
(B) Lead-time bias
(C) Length bias
(D) Measurement bias
(E) Recall bias

[Novobiocin]

(E) Recall bias since parents of autistic children are more likely to blame the vaccination to autism.

[step_enhancer]

Answer A Confounding

Autism has a genetic basis ,though there may be a difference in vaccination among different children.But real cause is genetic factor and the parent will tend to blame the vaccination for autism.
So here genetic is an unknown confounding factor here

[step1an]

D. Measurement bias.
The researcher is not blinded.

[rocketprinciple]

A.

As an instinct I was going to jump to 'E. Recall', but IMHO, vaccinations are 'ALWAYS' documented, So there's absolutely no question of Recall being the right answer, not so sure about the rest, besides I agree with step_enhancer above.

ALSO, If the vaccine is not documented, it's not considered given! Hence you can't forget about the fact wether it was given or not!!!
See the irony!!!