Choose a t-test for each situation: one-sample t-test, twosample t-test, paired t-test, and no t-test. 

a. A random sample of car dealerships is obtained. Then a student walks onto each dealer’s lot wearing old clothes and finds out how long it takes (in seconds) for a salesperson to approach the student. Later the student goes onto the same lot dressed very nicely and finds out how long it takes for a salesperson to approach. 

b. A researcher at a preschool selects a random sample of 4-year-olds, determines whether they know the alphabet (yes or no), and also records gender. 

c. A researcher calls the office phone for a random sample of faculty at a college late at night, measures the length of the outgoing message, and records gender.