A researcher trains observers to complete checklists while observing children's behavior on the schoolyard during recess. Over the course of the study, observers become more reliable in their observations. Any effect of a treatment in this study might be confounded with an threat to internal validity.

expectancy effect

Explanation:            

Expectancy effect: In psychology, the term "expectancy effect" is described as the result that an experimental observer or researcher tends to generate when he or she is somehow, subconsciously or subtly, transmitted the "expected results" related to the participant.

In other words, it represents the subconscious effect of an experimenter on the test or study participants.

In the question above, the given statement signifies the expectancy effect.

aristocracy, timocracy, oligarchy, democracy, theocracy and tyranny

explanation:

the chart shows a production possibilities schedule for sabrina’s soccer.

the schedule shows the - combination-   of goods the business can produce.

for edgenuit.