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# The regression equation is bld pres 540 106 drug tkr

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The regression equation is Bld Pres = 54.0 + 10.6 Drug Tkr + 0.139 weight Predictor Coef Stdev t-ratio p Constant 54.040 8.927 6.05 0.000 Drug Tkr 10.596 2.984 3.55 0.004 weight 0.13950 0.05248 2.66 0.021 s = 4.418 R-sq = 81.2% R-sq(adj) = 78.0% Analysis of Variance SOURCE DF SS MS F p Regression 2 1009.06 504.53 25.84 0.000 Error 12 234.27 19.52 Total 14 1243.33 b) If the first 9 people in the data set were those who did not take the drug, and the last 6 were those who did, write down the column of data you would input for the variable “Drug Tkr.” c) Using the results of the multiple regression, compute a 95% confidence interval for the impact of the drug on blood pressure. d) The answers you got in parts (b) and (c) are not the same, nor should they be, because they measure subtly different things. Explain the difference. e) In the regression above, what is the estimated variance of the regression’s error term? 18) A frustrated web surfer is annoyed with the long delays in downloading material from the World Wide Web (or World Wide Wait, as it is also known.) He gets the idea that it might be quicker to do his surfing in the morning, while users on the West Coast are still asleep. To test the hypothesis that things should be quicker in the morning, he selects 6 web pages and measures the waiting time to access each one in the morning, and then to access the same pages in the afternoon. This is his data: Web Site Wait in morning Wait in Afternoon ST “First Contact” 45 seconds 62 seconds Virgo 12 seconds 13 seconds Baywatch 30 seconds 35 seconds Whitehouse.gov 21 seconds 26 seconds Whitehouse.net 42 seconds 35 seconds Monty Python 32 seconds 43 seconds Is this convincing evidence that web surfing is quicker in the morning? Use .10 α = . a) Write down the null and alternative hypotheses, being sure to use the correct notation.

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b) Perform an appropriate test of the hypothesis. Do you accept or reject the null hypothesis? 19) a) Suppose you come across a report of an experiment done to determine the value of anti-lock brakes in preventing collision damage to automobiles. According to the report, 800 prospective buyers of a particular brand of car that does not ordinarily have anti-lock brakes were randomly assigned to either a control or treatment group. The buyers in the control group received the ordinary version of the automobile, while the buyers in the treatment group were given anti-lock brakes as a free option in an otherwise identical car. After 5 years, the 400 buyers in the control group had experienced accidents with an average collision damage of \$688 and a standard deviation of \$250, while the 400 buyers in the treatment group experienced accidents with an average collision damage of \$625 with a standard deviation of \$220. Perform a hypothesis test to see whether this is convincing evidence that anti-lock brakes reduce collision damage.
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