In the past the yield of a certain crop, in tonnes per hectare, had mean 0.56 and standard deviation 0.08. Following the introduction of a new fertilizer, the farmer intends to test at the 2.5% significance level whether the mean yield has increased. He finds that the mean yield over 10 years is 0.61 tonnes per hectare.
- (a)State two assumptions that are necessary for the test.[2]
- (b)Carry out the test.[5]
Mark scheme
Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.
- [B1] Assume standard deviation unchanged or standard deviation = 0.08
- [B1] Assume yields normally distributed
- [B1] Ho: Population mean yield (or μ) = 0.56
- [B1] H1: Population mean yield (or μ) > 0.56
- [M1] (0.61-0.56) / (0.08/√10)
- [A1] 1.976
- [M1] Comp 1.96
- [A1] There is evidence that mean yield has increased
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