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# q6s - The SD is 0.5 either from the box 1 or from √ 53 ×...

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Math 127B, Quiz 6. Key. Thursday, March 17th, 2011 Name: Recitation Section: Ten minutes. Calculators allowed. 20 points maximum. 1. A coin is tossed 400 times. It lands heads 212 times. [ 20 points] (a) Based on this do you believe that there is evidence to support the claim that the coin is biased, i.e., not fair. Clearly state all the details of your test of signiﬁcance. The expected percentage of heads is 50% under the null hypothesis. The alternative is that the coin is not fair. this may or may not be a box model. If the coins properties change with each toss, then they are not independent.
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Unformatted text preview: The SD is 0.5, either from the box 1 or from √ . 53 × . 47. The SE of the number is √ 400 × . 5 = 10. The SE of the percentage is 10 / 400 × 100% = 2 . 5%. The score is z = (53-50) / 2 . 5 = 1 . 2. You can also do z = (212-200) / 10 = 1 . 2. The P-value is 12%. This is not signiﬁcant. We put the diﬀerence down to chance variation. (b) How does your answer change if instead it had landed tails 212 times? It doesn’t. Heads and tails are interchangeable in this problem under the assumption that the coin is fair! 1...
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