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Unformatted text preview: 33 (one-tailed), or 2.58 (two-tailed). In either case these
results are easily significant at the .01 level. Because the sample size was 4 times
larger for part b than part a, the z-score from part a could have been simply multiplied
by 2 (i.e., the square-root of 4).
1. a) 2.7
x 25 ; X z crit x = 96.08 ± 1.96 (.54); so, = 96.08 ± 1.06 Therefore, the 95% CI goes from 95.02 to 97.14 (note, as a check, that the sum of these two limits is
192.16, which is exactly twice as large as the sample mean, as will always be the case). Because the
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- Fall '12