A researcher becomes aware that the judges he is using to make observations are becoming more proficient at their task. This improvement among the judges might suggest that __________ represents a potential threat to the internal validity of the study.
a. instrumentation
b. history
c. maturation
d. selection
Question 2
While conducting a year-long study on friendship patterns in the sixth grade, a researcher discovers that some of the students had reached puberty during that year while others had not.
Which potential threat to internal validity would this example illustrate according to Campbell and his colleagues?
a. selection
b. instrumentation
c. maturation
d. history
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