Mathematics 9709 · AS & A Level · Hypothesis testing

Hypothesis testing — practice question

At one large school, it was discovered that the fraction of students who were not wearing the correct uniform was $0.15$. A letter was then sent to parents, requesting that they make sure their children wear the correct uniform. The school now wants to check whether the fraction not wearing the correct uniform has gone down.
(a)[1]

It is suggested that a random sample of the students in Grade 12 should be used for the test. Give a reason why this would not be a suitable sample.

(b)[1]

A suitable sample of 50 students is chosen and the number not wearing the correct uniform is recorded. This result is then used to perform a test at the $5\%$ significance level. State suitable null and alternative hypotheses.

(c)[5]

Use a binomial distribution to determine the probability of a Type I error. Your answer must be fully justified.

(d)[2]

In fact, 4 students out of the 50 are not wearing the correct uniform. State the conclusion of the test, with an explanation.

(e)[2]

State, with a reason, which error, Type I or Type II, may have occurred.

Worked solution & mark scheme

This 11-mark question has a full step-by-step worked solution and mark scheme. One marking point: The sample would not represent all students in the school.

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