For each of the following operational definitions, decide whether you consider it to be a valid measure. Explain why or why not. Decide whether you consider it to be a reliable measure. Explain why or why not.
a. A researcher defines social anxiety in terms of the number of minutes before a child begins to interact with adults other than his or her parents.
b. A professor classifies students as either introverted or extroverted based on the number of questions each individual asks during one week of class.
c. A sports psychologist measures physical fitness by measuring how high each person can jump.
d. Reasoning that bigger brains require bigger heads, a researcher measures intelligence by measuring the circumference of each person’s head (just above the ears).