18 In a region of England, the government decides to use an advertising campaign to encourage people to eat more healthily.
Before the campaign, the mean consumption of chocolate per person per week was known to be 66.5 g , with a standard deviation of 21.2 g
18
- After the campaign, the first 750 available people from this region were surveyed to find out their average consumption of chocolate.
18
- State the sampling method used to collect the survey.
18
- (ii) Explain why this sample should not be used to conduct a hypothesis test.
18 - A second sample of 750 people revealed that the mean consumption of chocolate per person per week was 65.4 g
Investigate, at the \(10 \%\) level of significance, whether the advertising campaign has decreased the mean consumption of chocolate per person per week.
Assume that an appropriate sampling method was used and that the consumption of chocolate is normally distributed with an unchanged standard deviation.
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