A gang of criminals is planning to rob a supermarket. Annie, the gang leader, reports that she staked the store out the day before and saw the store detective going for a 15 minute coffee break at 9:15 a.m. She suggests that this would be the best time to strike. Clive, a gang member, thinks that this plan is too riskyhow do they know that the detective takes his break at the same time each day? Annie, who is desperate for money, thinks the plan is safe enough and wants to carry out the robbery the next day. After an argument, they agree to compromise and watch the supermarket for three more days. On each of the three days, the store detective indeed takes his 15 minute break at 9:15 a.m. The gang decides to go ahead with the robbery on the fourth day.

The robbers can be seen as having set themselves up with a research question and having made a statistical decision based on a simple study.

a) In words, what are the robbers' null and alternate hypotheses?

b) Based on these hypotheses, what is their decision? (i.e. Did they reject or fail to reject the null hypothesis?)

c) What type of statistical error should the robbers be most concerned with making (type I or II)? Explain.