What assumptions do scientists make when they use one measurement to find another

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

regents of the university of california v. bakke, 438 u.s. 265 (1978), was a landmark decision by the supreme court of the united states. it upheld affirmative action, allowing race to be one of several factors in college admission policy.