What is the primary threat to validity? Please use each of the following only once: Mortality/Attrition, Selection, History, Maturation, Testing Mechanisms, and Instrumentation Threat. (Pl

What is the primary threat to validity?
Please use each of the following only once: Mortality/Attrition, Selection, History, Maturation, Testing Mechanisms, and Instrumentation Threat. (Please use at least one source)
A study of the effect of patient education on compliance with an oral hygiene program uses two groups: patients attending the out-patient clinic and those seeing their private hygienists/dentists.
(These are the other questions that are in the assignment, so it may make choosing the correct easier)
During an obstetrical study of socioeconomic status on complication rates of normal deliveries, the state legislature passes a bill requiring 48 hour hospital stays for new mothers.
A study of the effect of a critical-thinking workshop on dieticians’ decision-making skills uses a complex series of simulations (patient management problems) as the pre- and post-tests.
A study is assessing the effect of a procedure on patients’ long-term improvements in post-operative pulmonary function after undergoing complex transplant surgery.
In a study of the effect of participation in a rehabilitation program on patients’ activities of daily living, 40% of the patients do not complete the program.
A researcher studying the long-term effects of a new Alzheimer’s disease drug on mental function has family members rate the patients’ on a cognition scale developed “in-house.”
A study of the effect of patient education on compliance with an oral hygiene program uses two groups: patients attending the out-patient clinic and those seeing their private hygienists/dentists.