Experiments on learning in animals sometimes measure how long it takes a mouse to find its way through a maze. The mean time is 18 seconds for one particular maze. A researcher thinks that a loud noise will cause the mice to complete the maze faster. She measures how long each of 10 mice takes with a noise as stimulus. Choose the correct null hypothesis H0 and alternative hypothesis Ha from the choices below.

a) H0: µ = 18; Ha: µ < 18.
b) H0: µ = 18; Ha: µ > 18.
c) H0: y = 18; Ha: y < 18.
d) H0: y = 18; Ha: y > 18.
e) H0: µ = y; Ha: µ < y.
f) H0: y = 18; Ha: y ? 18.
g) H0: µ = 18; Ha: µ ? 18.