Healthy-Greens Farm grows organic cucumbers. They are considering a new irrigation system and hope it will increase the average yield per plant by at least 1.5 kg. The variance of the yield using the existing system is 0.6 kg2, and the variance of the yield using the new system is 0.8 kg2. A random sample of 50 plants using the existing system has a mean yield of 6.2 kg. A random sample of 80 plants using the new system has a mean yield of 8.1 kg.
Stating your hypotheses clearly, test at the 5% level of significance whether or not there is evidence that the mean yield with the new system is more than 1.5 kg greater than the mean yield with the existing system.
Explain the relevance of the Central Limit Theorem to the test conducted in part (a).
316 exam-style questions on OCR A Level Maths 2.5 Statistical Hypothesis Testing, covering 2.5.1 The language of hypothesis testing, 2.5.2 Hypothesis test for a binomial proportion, 2.5.3 Inference and significance level, 2.5.4 Sample mean as a random variable (A-level only), 2.5.5 Hypothesis test for the mean of a normal distribution (A-level only), 2.5.6 Pearson's product-moment correlation coefficient, and 2.5.7 Hypothesis test using Pearson's coefficient (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.