I found an I.Q. score question that has been bothering me: If the population mean is 100, the standard deviation is 10, and given a sample of six scores, what is the probability that three of the scores are less than 90, two are between 90 and 120, and one is greater than 120. Can this problem be solved without using Z-scores, using instead the pdf formula for the normal distribution.
What I immediately thought was: $P(X<90)^3 * P(90<X<120)^2 * P(X>120)$, again using the pdf function for the normal distribution.
Is this logical?