Methods Week 9 - Meta-analysis examples (2/2)

fail safe N

N = number of studies

number of unpublished, non-significant studies which would have to exist in researchers’ fling cabinets in order to render the meta-analysis non-significant.

critical number of studies

number of unpublished, non-significant studies which we could reasonably expect to be “filed away”.

• If critical number of studies is greater than or equal to the fail-safe N, we potentially have a “file-drawer problem”.

what is a funnel plot

A funnel plot is a scatterplot of treatment effect against a measure of study precision. It is used primarily as a visual aid for detecting bias or systematic heterogeneity

if it makes a triangle it means no publication bias

at small sample sizes, you are expecting large variety 

if it makes a half triangle then there is a publication bias

only see publications that have high effect scores

if the study is weighted heavily (more participants) is your CI smaller or larger

smaller

meta regression

explain this regression meta-analysis (hedge’s g = bigger difference between healthy and ADHD individuals)

the older the individual is, the better they do on working memory if they have ADHD compared to a healthy adult.

• the older the patients with ADHD get, the less studies there are