Question: An experimenter claims that the average yield of extracting protein per 50 kg of seaweed is over 4 kg while using in animal feed. It is known that the yield of extracting protein is normally distributed. To support his claim, a sample of 16 determination of protein extract, each based on 50 kg of seaweed, is analyzed. The results yield a sample mean of 4.2 kg and a sample standard deviation of 0.8 kg.

a. Do the results support the experimenter's claim? Test at 0.1 level of significance.

b. Do we have sufficient evidence to support that the variance of the yield of protein extract per 50 kg of seaweed is less than 1.5? Test at 0.05 level of significance.