Miriam is using a one-sample t-test on the following group:

Subject #15: 6.5 hours

Subject #27: 5 hours

Subject #48: 6 hours

Subject #80: 7.5 hours

Subject #91: 5.5 hours

Select the two TRUE statements.

a) The t-distribution that Miriam uses is shorter and has thicker tails than a normal distribution.

b.) The t-distribution that Miriam uses is taller and has thinner tails than a normal distribution.

c.) The value for the degrees of freedom for Miriam's sample population is five.

d.) The value for the degrees of freedom for Miriam's sample population is four.

e.) Miriam needs to use a t-test when the standard deviation is known.