Which of the characteristics below distinguishes the t statistic from the z statistic?
a. the proportion of area beyond a particular positive t value is equal to the proportion of area below the corresponding negative t
b. the z distribution has a mean of zero while the t distribution does not
c. In the t distribution the area under the curve beyond a value of 1.96 is greater than that of the normal curve
d. all of these
Question 2
In a t test, when the size of the sample is increased, the confidence interval _________.
a. increases c. stays the same
b. decreases d. changes shape