Using more than one measure of the same variable, such as using a survey and direct observation, is known as

Triangulation

Step-by-step explanation:

Triangulation is a method used in research to ensure that the results obtained are credible. This means that triangulation is aimed at ensuring that the outcome of the research is dependable and reliable. The method combines several theories or methods to arrive at a result.

This would help to ensure that the research has a high degree of accuracy and can be verified by any scientist. So, using more than one measure of the same variable in research is triangulation.

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.