Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A smoke alarm can be thought of as a test, with the null idea "there is no fire". The alarm sounds when there is no fire. Which kind of error is this? Later, a real fire starts and the alarm stays silent. Which kind of error is that? A study uses . If its null idea is true, what is the probability of a Type I error?
Reject the null idea when the p-value is at most . A Type I error is a false alarm and a Type II error a missed effect. Among independent tests of true null ideas, the chance of at least one false alarm is .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Sounding with no fire rejects a true null idea: a Type I error, a false alarm.
Step 2. Staying silent in a fire fails to reject a false null idea: a Type II error, a missed effect.
Step 3. When the null idea is true, a Type I error happens with probability .
Answer: Type I, Type II, and . A smoke alarm is set to be very sensitive, because a missed fire is far worse than a false alarm.
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