Two primary considerations in psychological measurement are validity and reliability. Without both, the results of a psychological study are meaningless. Explain the concepts of validity and reliability. Define internal and external validity, and give an example illustrating each.

1) Validity: This concept takes into consideration if the test truly measures what it intends to. There are two types of validities: internal and external validity.

The first one considers the minimum conditions to ensure the interpretation of the data obtained (ex: A test being able to relate a low IQ with a particular learning disorder) whereas the second one considers the minimum conditions to ensure the generalization of the conclusions (ex: The relation between low IQ and that particular learning disorder is always present)

2) Reliability: Considers if the test is able to obtain interpretable data while being administrated on the same conditions everytime.