A strength of van Ijzerndoorn and Kroonenbergâs study into cultural variations in attachment is its large sample size. The meta-analysis included 32 studies from 8 countries and analysed attachment data from nearly 2,000 children. This strengthens the study as a large sample size increases the internal validity, as well as the reliability and generalisability of the findings. Also, by using many studies, they reduced the influence of anomalies in individual studies.