Standard +0.3 This is a straightforward one-tailed Poisson hypothesis test with clear context. Students must formulate H₀: λ=5 vs H₁: λ<5, find P(X≤1) under H₀, and compare to 5%. The calculation is routine (using tables or formula) with no conceptual tricks, making it slightly easier than average but requiring proper hypothesis test structure.
2. An effect of a certain disease is that a small number of the red blood cells are deformed. Emily has this disease and the deformed blood cells occur randomly at a rate of 2.5 per ml of her blood. Following a course of treatment, a random sample of 2 ml of Emily's blood is found to contain only 1 deformed red blood cell.
Stating your hypotheses clearly and using a \(5 \%\) level of significance, test whether or not there has been a decrease in the number of deformed red blood cells in Emily's blood.
2. An effect of a certain disease is that a small number of the red blood cells are deformed. Emily has this disease and the deformed blood cells occur randomly at a rate of 2.5 per ml of her blood. Following a course of treatment, a random sample of 2 ml of Emily's blood is found to contain only 1 deformed red blood cell.
Stating your hypotheses clearly and using a $5 \%$ level of significance, test whether or not there has been a decrease in the number of deformed red blood cells in Emily's blood.\\
\hfill \mbox{\textit{Edexcel S2 2009 Q2 [6]}}