2022 DHS P2 Q9

2022 DHS P2 Q9

9 marks
Prelims
  1. A confectionery is selling mooncakes during the Mid-Autumn Festival. The owner claims that the mean mass of the mooncakes is at least \(150\) g. The distribution of the mass of a mooncake has standard deviation \(6.73\) g. A customer bought a random selection of \(9\) mooncakes from the confectionery with masses, in g, as follows:

    \(145\)    \(148\)    \(153\)    \(156\)    \(141\)    \(151\)    \(143\)    \(157\)    \(138\)
    Test at the \(10\%\) significance level whether the owner’s claim is valid. State an assumption about the population distribution of the mass of the mooncakes.[5]
  2. In a particular country, the mean working hours of teachers in schools is \(60\) hours per week. After implementation of the Home-Based Learning in all schools, the Ministry claims that the mean working hours of teachers remained unchanged. A random sample of \(50\) teachers was taken and the number of working hours per week was recorded. The mean working hours and standard deviation for the sample were found to be \(62\) hours and \(k\) hours respectively. A hypothesis test was conducted and it was found that there is sufficient evidence to reject the Ministry’s claim at \(5\%\) significance level. Find the set of values of \(k\).[4]

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Answer:(a) From GC, \({p\text{}\hspace{0.5em}-\text{ value} = 0.186}\) (\(3\) s.f.) Since the \({p\text{}\hspace{0.5em}-\text{ value} > 0.1}\), we do not reject \({H_0}\) and conclude that there is insufficient evidence at the \({10\%}\) significance level that the mean mass of the mooncake is less than \({150\text{ g}}\), i.e. insufficient evidence to reject owner's claim. (b) Set of values of \({k}\) is \({\{k \in \mathbb{R} : 0 < k \leq 7.14\}}\)

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