Psychological experiment on alcohol and threats. A group of Florida State University psychologists examined the effects of alcohol on the reactions of people to a threat (Journal of Abnormal Psychology, Vol. 107, 1998).
After obtaining a specified blood alcohol level, experimental subjects were placed in a room and threatened with electric shocks. Using sophisticated equipment to monitor the subjects' eye movements, the startle response (measured in milliseconds) was recorded for each subject. The mean and standard deviation of the startle responses were 37.9 and 12.4, respectively. Assume that the startle response y for a person with the specified blood alcohol level is approximately normally distributed.
(a) Find the probability that y is between 40 and 50 milliseconds.
(b) Find the probability that y is less than 30 milliseconds.
(c) Give an interval for y, centered around 37.9 milliseconds, so that the probability that y falls in the interval is .95.