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.

well, paralell is parallel. i am providing links to .

hope this !

a series circuit is one with all the loads in a row. there is only one path for the electricity to flow. if this circuit was a string of light bulbs, and one blew out, the remaining bulbs would turn off.

unlike in series circuits, a charge in a parallel circuit encounters a single voltage drop during its path through the external circuit. the current through a given branch can be predicted using the ohm's law equation and the voltage drop across the resistor and the resistance of the resistor.

a parallel circuit has certain characteristics and basic rules: a parallel circuit has two or more paths for current to flow through. voltage is the same across each component of the parallel circuit.