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Unformatted text preview: at the 5% significance level.
Therefore, I conclude that adult males have not gotten taller since 1900. Final Practice Problems – Free Response  Answers
Question 3
In 1988, 75% of American children age 11 and younger went trickortreating on Halloween. After
Halloween 2011, 175 American children age 11 and younger were randomly surveyed. 112 of them
reported that they had gone trickortreating.
a) Estimate the true proportion of American children that went trickortreating in 2011 with 90%
confidence. ̂ ( ̂) √ ̂( ̂) ( √ ( ̂)
̂ ) ( ) [0.581, 0.699]
I am 90% confident that the true proportion of American children that went trickortreating
in 2011 is between 0.581 and 0.699.
b) Does this provide evidence that trickortreating has become less popular? Use a 5% significance
level. ̂ (from part a) () √ ( ) √ ̂
() ( ) Final Practice Problems – Free Response  Answers ( ) The results are statistically significant at the 5% significance level. Therefore, I reject the null
hypothesis and conclude that trickortreating has declined in popularity since 1988....
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 Spring '11
 miyagi

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