Final answer:
The rational basis test is used for age discrimination for equal protection purposes; strict scrutiny is applied for cases involving race, ethnicity, or national origin, and intermediate scrutiny for gender or sex-based discrimination.
Step-by-step explanation:
For equal protection purposes concerning age discrimination, the standard used to determine the constitutionality of a government action is the rational basis test. Under this test, the burden of proof is on those challenging the law or action to demonstrate there is no reasonable justification for the disparate treatment they are receiving. In contrast, strict scrutiny is applied in cases involving discrimination based on race, ethnicity, or national origin, where the government must prove a compelling governmental interest to justify the discrimination. The intermediate scrutiny standard is used for discrimination based on gender or sex, requiring the government to show that the unequal treatment is substantially related to an important government objective.