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A news report says: "In a random poll, 45% of voters back the new road, with a margin of error of 4…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A news report says: "In a random poll, of voters back the new road, with a margin of error of points." Give the lower and the upper ends of the interval, in percent. A reader says the poll shows that half the voters might back the road. Is the reader right?
Need a reminder? The key ideaShow
The margin of error for confidence is standard errors. For a share, . The interval is the estimate plus or minus the margin.
The worked solution
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. and .
Step 2. The value is above the upper end, .
Answer: from to . The reader is not right: a share of one half lies outside the interval, so the poll does not support it at the level.
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