Some of the threats to internal validity in research are which of the following?

Attrition, history, and maturation are classic threats to the internal validity of a study.

Attrition is the loss of participants over time, which can bias group comparisons.

History refers to outside events during the study that affect the outcome.

Maturation is natural change within participants, such as growing older or more tired.

Quasi-experimental design is a research design, not itself a threat to internal validity.

Selection, testing, instrumentation, and regression to the mean are further recognised threats.