Statistics - explanations and formulas

Internal Validity and External Validity

Internal validity

Internal validity refers to the accuracy or truth of the study results which depends on how well the design, implementation, and statistical analysis have minimized or eliminated bias.

The factors that can effect internal validity are randomization, groups being equal at baseline, each group having the same treatment asides from the treatment under study,  good follow up with a low dropout rate (typically less than 15%) , blinding of participants and investigators and intention to treat analysis.

This study had high internal validity.


External validity

External validity of a study is the degree to which the findings are able to be generalized to other groups or populations. This study has high external validity as most children we see in primary care have mild dehydration.