Never forget that even small effects can be statistically significant if the samples are large. To illustrate...

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Never forget that evensmall effects can be statistically significant if the samples arelarge. To illustrate this fact, consider a sample of 104 smallbusinesses. During a three-year period, 10 of the 71 headed by menand 6 of the 33 headed by women failed.

(a) Find the proportions of failures for businesses headed bywomen and businesses headed by men. These sample proportions arequite close to each other. Give the P-value for the test of thehypothesis that the same proportion of women's and men's businessesfail. (Use the two-sided alternative). What can we conclude (Use?=0.05?=0.05)?
The P-value was so we conclude that
Choose a conclusion.The test showed strong evidence of asignificant difference.The test showed no significantdifference.

(b) Now suppose that the same sample proportion came from asample 30 times as large. That is, 180 out of 990 businesses headedby women and 300 out of 2130 businesses headed by men fail. Verifythat the proportions of failures are exactly the same as in part(a). Repeat the test for the new data. What can we conclude?
The P-value was so we conclude that
Choose a conclusion.The test showed strong evidence of asignificant difference.The test showed no significantdifference.

(c) It is wise to use a confidence interval to estimate the sizeof an effect rather than just giving a P-value. Give 95% confidenceintervals for the difference between proportions of men's andwomen's businesses (men minus women) that fail for the settings ofboth (a) and (b). (Be sure to check that the conditions are met. Ifthe conditions aren't met for one of the intervals, use the sametype of interval for both)
Interval for smaller samples:___ to ___
Interval for larger samples: ___to ___

What is the effect of larger samples on the confidenceinterval?
Choose an effect.The confidence interval is unchanged.Theconfidence interval's margin of error is reduced.The confidenceinterval's margin of error is increased.

Answer & Explanation Solved by verified expert
4.4 Ratings (720 Votes)
a The hypotheses areThe sample proportions areThe pooled proportion isThe test statistic isThe two tailed pvalue isSince pvalue is greater than fail toreject the null    See Answer
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SALARY EDUC EXPER TIME 39000 12 0 1 40200 10 44 7 42900 12 5 30 43800 8 6 7 43800 8 8 6 43800 12 0 7 43800 12 0 10 43800 12 5 6 44400 15 75 2 45000 8 52 3 45000 12 8 19 46200 12 52 3 48000 8 70 20 48000 12 6 23 48000 12 11 12 48000 12 11 17 48000 12 63 22 48000 12 144 24 48000 12 163 12 48000 12 228 26 48000 12 381 1 48000 16 214 15 49800 8 318 25 51000 8 96 33 51000 12 36 15 51000 12 59 14 51000 15 115 1 51000 15 165 4 51000 16 123 12 51600 12 18 12 52200 8 102 29 52200 12 127 29 52800 8 90 11 52800 8 190 1 52800 12 107 11 54000 8 173 34 54000 8 228 33 54000 12 26 11 54000 12 36 33 54000 12 38 22 54000 12 82 29 54000 12 169 27 54000 12 244 1 54000 15 24 13 54000 15 49 27 54000 15 51 21 54000 15 122 33 55200 12 97 17 55200 12 196 32 55800 12 133 30 56400 12 55 9 57000 12 90 23 57000 12 117 25 57000 15 51 17 57000 15 61 11 57000 15 241 34 60000 12 121 30 60000 15 79 13 61200 12 209 21 63000 12 87 33 63000 15 231 15 46200 12 12 22 50400 15 14 3 51000 12 180 15 51000 12 315 2 52200 12 29 14 54000 12 7 21 54000 12 38 11 54000 12 113 3 54000 15 18 8 54000 15 359 11 57000 15 36 5 60000 8 320 21 60000 12 24 2 60000 12 32 17 60000 12 49 8 60000 12 56 33 60000 12 252 11 60000 12 272 19 60000 15 25 13 60000 15 36 32 60000 15 56 12 60000 15 64 33 60000 15 108 16 60000 16 46 3 63000 15 72 17 66000 15 64 16 66000 15 84 33 66000 15 216 16 68400 15 42 7 69000 12 175 10 69000 15 132 24 81000 16 55 SUMMARY OUTPUT Regression Statistics Multiple R 0.41198516 R Square 0.16973178 Adjusted R Square 0.16060795 Standard Error 6501.12045 Observations 93 ANOVA df SS MS F Significance F Regression 1 786253429 786253429 18.60313 4.08E-05 Residual 91 3.85E+09 42264567.1 Total 92 4.63E+09 Coefficients Standard Error t Stat P-value Lower 95% Upper 95% Lower 95.0% Upper 95.0% Intercept 38185.5979 3774.3766 10.117061 1.45E-16 30688.26252 45682.93 30688.26 45682.93 X...