What are the three threats to internal validity associated with measurement?

What will be an ideal response?

(a) Instrumentation–the actual equipment may need calibration after a time, especially mechanical devices; in addition, the researcher may inadvertently change scoring procedures in a way that makes later scores different from earlier scores.
(b) Testing–participants' behaviors change because they become sensitized to the study with repeated testing
(c) Statistical regression (Regression to the mean)–If tested at the beginning of a study and at the end, initial scores may be artificially high or low because of measurement error; this error is not likely to persist, so scores migrate back where they "belong".