Edexcel A-Level Mathematics A2 S2.4.4 Critical Region Questions

Practise determining a critical region by comparing tail probabilities with a significance level, then state the accepted statistic boundary clearly.

Exam points

use the test-statistic distribution and significance level to determine a critical boundary, such as J ≥ 15 for a Po(9) test at 5%

[Maximum number: 2]

The number of cars entering a safari park per 10 -minute period can be modelled, by a Poisson distribution with mean 6

Determine the critical region for the test at the 5\% level of significance.

$J\sim \operatorname{Po}(9)$ $P(J\le 13)=0.9261$ $P(J\le 14)=0.9585$

So the critical region is $J\ge 15$ .

Marking guidance for 4(f):
M1 for writing or using $\operatorname{Po}(9)$ , implied by a correct critical region.
A1 cao. Allow J>14. Do not allow as part of a probability statement.

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Edexcel A-Level Mathematics A2 S2.4.4 Critical Region Questions question 1