Suppose that the time that owners keep their cars (purchased new) is normally distributed with a mean of 7 years and a standard deviation of 2 years. We are interested in how long an individual keeps his car (purchased new). Our population is people who buy their cars new.
Compare the standard normal distribution to the student-t distribution, centered at 0. Explain which of the following are true and which are false.
a. As the number surveyed increases, the area to the left of -1 for the student-t distribution approaches the area for the standard normal distribution.
b. As the degrees of freedom decrease, the graph of the student-t distribution looks more like the graph of the standard normal distribution.
c. If the number surveyed is 15, the normal distribution should never be used.