A psychiatrist believes that \(80 \%\) of all people who visit doctors have
problems of a psychosomatic nature. She decides to select 25 patients at
random to test her theory.
a. Assuming that the psychiatrist's theory is true, what is the expected value
of \(x\), the number of the 25 patients who have psychosomatic problems?
b. What is the variance of \(x\), assuming that the theory is true?
c. Find \(P(x \leq 14)\). (Use tables and assume that the theory is true.)
d. Based on the probability in part \(\mathrm{c}\), if only 14 of the 25 sampled
had psychosomatic problems, what conclusions would you make about the
psychiatrist's theory? Explain.