1. A magazine conducted a survey about the sleeping time of adults. A random sample
of 12 adults were chosen from the adults travelling to work on a train.
a. Give reason why this is an unsatisfactory sample for the purpose of the study.
b. State a population for which this sample would be satisfactory.
2. A machine is designed to make paperclips with mean mass 4.00g and standard
deviation 0.08. The distribution of the masses of the paperclips is normal. A quality
controller weighs a random sample of 25 paperclips and find their total mass to be
101.2g.
a. Describe the use of hypothesis testing in real world.
b. Conduct a hypothesis test at 5% significance level to test whether this provides
evidence of an increase in the mean mass of the paperclips.
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