21. Laboratory rats commit an average of  40 errors before they solve a standardized maze problem. The distribution of error scores is approximately normal with a standard deviation of  8. A researcher is testing the effect of a new dietary supplement on intelligence. A newborn rat is selected and is given the supplement daily until it reaches maturity. The rat is then tested on the maze and finishes with a total of X 24 errors.

a. What is the probability that a regular rat (without the supplement) would solve the maze with a score less than or equal to X 24 errors?

b. Is it reasonable to conclude that the rat with the supplement is smarter than the vast majority of regular rats?

c. Does it appear that the supplement has an effect on intelligence? Explain your answer.