P- One strength is that it has a large sample
E- this is because the combination of results of attachment studies carried out in different countries.In the meta-analysis carried out there is over 2000 babies and their primary caregiver attachment figures
E- Also, the Simonella and Jin studies had larger comparison groups from previous research, although their own samples were smaller
L- therefore, this means that it has high population validity and can be easier to extrapolate findings back to the target population regarding attachment types
C- however, it is more generalisable in America rather an other countries due to the multiple studies, even though there is generalisability America is a large country which means that there is more variation within the country and it may not be representative of/generalisable back to it fully