Internal validity: refers both to how well a study was run (research design, operational
definitions used, how variables were measured, what was/wasn't measured, etc.), and how
confidently one can conclude that the observed effect(s) were produced solely by the
independent variable and not extraneous ones.
Internal validity threat: Threats that compromise confidence of the relationship existing
between two variables.
E.g. Arthritis being associated to aging.
o Difference in the sample groups of individuals. One group lived in an environment that
prevents arthritis while other doesn’t.
o responses u get might now be accurate
o Hawthorne effect: thought that because you are present in study you behave in the way
you think you are expected to behave in the study. i.e. alteration in behaviour of subject
due to them being observed
o Mood bias: low spirited people might underestimate responses to health status because
of current mood
External Validity: represents the extent to which a study's results can be generalized or applied
to other peo