3. (9 points) Suppose we are interested in learning about the average crop yield of wheat when adding a
new change to the soil conditions. To do so, we formed 25 plots of land and measured the total yield
per plot in kg. We will assume that X1,..., X25 follow the normal distribution with an unknown mean
µ and standard deviation of 1 ton. Suppose we wish to test Ho: µ = 4 tons, and HA: μ > 4 tons at
level a = 0.05.
(a) (3 points) Do we need the Xi's to be normally distributed in order to conduct the appropriate
hypothesis test in this case? And should we conduct a T or Z test?
(b) (6 points) Suppose we define a hypothesis test by the rejection region where we reject the null
hypothesis Ho when X > 5 tons. What is the significance level of this new test?