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TAMU STAT 303 - ex2asp11

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STAT303 Sec 508-510Spring 2011Exam #2Form AInstructor: Julie Hagen CarrollName:1. Don’t even open this until you are told to do so.2. All graphs are on the last page which you may remove.3. There are 20 multiple-choice questions on this exam, each worth 5 points. There is partial credit. Please mark youranswers clearly. Multiple marks will be counted wrong.4. You will have 60 minutes to finish this exam.5. If you have questions, please write out what you are thinking on the back of the page so that we can discuss it afterI return it to you.6. If you are caught cheating or helping someone to cheat on this exam, you both will receive a grade of zero on theexam. You must work alone.7. This exam is worth the 15% of your course grade.8. When you are finished please make sure you have marked your CORRECT section (Tuesday 12:45 is 508, 2:20 is 509,and 3:55 is 510) and FORM and 20 answers, then turn in JUST your scantron to the correct pile for your section.9. Good luck!1STAT303 sec 508-510 Exam #2, Form A Spring 20111. Comparing the p-value to α is the same as comparingA. the critical (table) value to the test statistic.B. the sample mean to the hypothesized mean.C. the hypothesized mean to a confidence interval.D. Two of the above are correct.E. None of the above are correct.2. Suppose we have a 95% confidence interval for the truetest average, µ, of (73.6, 85.8). Then we can sayA. 95% of the test takers made a B (in the 80’s) or C(in the 70’s).B. 95% of all exams of this type will have an averagein this same range.C. 95% of the possible samples from this same pop-ulation of test grades will have an average in thisrange.D. 95% of the possible samples from this same pop-ulation of test grades will produce intervals con-taining this range.E. None of the above are correct.3. The test below compares the women’s labor force in1972 and 1968.Hypothesis test results:mu1 : mean of 1972, mu2 : mean of 1968mu1 - mu2 : mean differenceH0 : mu1 - mu2 = 0 vs. HA : mu1 - mu2 > 0(with pooled variances)Difference Sample Mean Std. Err. DF T-Stat P-valuemu1 - mu2 0.0337 0.0225 36 1.496 0.0717Which of the following is the correct conclusion?A. At the 10% level of significance, we can say thatthe women’s labor force changed from 1968 to1972.B. At the 1 and 5% levels, we can say that there isno change in the women’s labor force from 1968to 1972.C. At the 1 and 5% levels, we can say that there is adecrease in the women’s labor force from 1968 to1972.D. At the 10% level of significance, we can say thatthere is an increase in the women’s labor forcefrom 1968 to 1972.E. Two of the above are correct.4. Using the three confidence intervals below, what is thecorrect range of the p-value if I wanted to test H0: µ =8.5 vs. HA: µ 6= 8.5?90% (5.456, 8.004)95% (5.211, 8.248)99% (4.735, 8.725)A. p-value > 0.10B. 0.10 > p-value > 0.05C. 0.05 > p-value > 0.01D. p-value < 0.01E. You need a test statistic value to determine thep-value.5. Suppose I tested H0: µ = 5 vs. HA: µ 6= 5 with asample mean, ¯x = 7, sample size, n = 20 and standarddeviation, s = 2 from a normal population. In whichof the following situations would I be more likely toreject? Holding all other variables constant.A. a larger sample sizeB. a larger sample meanC. a larger sample µ0D. All of the above would have a smaller p-value, soI would be more likely to reject.E. Only two of the above would have a smaller p-value, so I would be more likely to reject.6. What are the missing values in the ANOVA table be-low? Remember that the median of an F distributionis 1.Location n Mean Std. ErrorAurora 200 14.34 0.24875973Denver 203 14.51 0.2827668Parker 224 14.125 0.26259512ANOVA tableSource df SS MS F-Stat P-valueTreatments 16.10 8.052ErrorTotal 9202.20A. num df = 3, den df = 623, F = 14.72, p-v is verysmallB. num df = 2, den df = 624, F = 14.72, p-v is verysmallC. num df = 2, den df = 624, F = 0.55, p-v > 0.50D. num df = 624, den df = 626, F = 0.55, p-v < 0.50E. Too many values are missing to fill them all incorrectly.7. Say we created 100 confidence intervals from 100 sam-ples of the same population. If we decrease the confi-dence level (99 to 95 to 90%),A. less of the intervals will contain the true mean.B. we will have more conservative intervals.C. we would have to take larger samples (increase n)to keep the widths the same.D. All of the above are correct.E. Two of the above are correct.8. Which of the following is/are true statements about theassumptions for hypothesis testing?A. The more assumptions we can make (valid as-sumptions), the greater power our test has.B. Assumptions give us the correct distribution forour data, so the p-value is correct.C. We always need to assume that the distribution ofthe sample mean, ¯x is normal.D. All of the above are correct.E. Only two of the above are correct.2STAT303 sec 508-510 Exam #2, Form A Spring 20119. Rejecting at the 5% significance level meansA. I will reject 5% of the time.B. I will also reject at the 1% significance level.C. I will make a Type II error 95% of the time sincethe probability of making a Type II error, β =1 − α.D. I don’t require ‘as much evidence’ to reject as Iwould at the 10% significance level.E. None of the above are correct.10. I want to test H0: µ1= µ2vs. HA: µ16= µ2, but all Ihave is a 95% confidence interval for the true differencein the population means.A. If 0 is the center of the interval, then µ1= µ2.B. If 0 is in the interval, then µ1= µ2.C. If 0 is in the interval, then ¯x1= ¯x2.D. Two of the above are true.E. None of the above are true.11. This data shows the Sales Per Week for 3 Ice CreamStores by Flavor of Ice Cream.Column n Mean Std. ErrorChocolate 628 14.85008 0.14720057Strawberry 628 20.01595 0.25493953Vanilla 628 14.318979 0.15287355ANOVA tableSource df SS MS F-Stat P-valueTreatments 2 12439.3 6219.68 270.03 <0.0001Error 1881 43326.0 23.03Total 1883 55765.3What is the correct conclusion for this test?A. Since we are not given the standard deviations, wecan’t say that the assumption of equal variancesis valid, so we can’t make any conclusions.B. Since the p-value is basically 0, there is no differ-ence (0 difference) in the sample means.C. Since the p-value is basically 0, there is no differ-ence (0 difference) in the true (population) means.D. Since the p-value is basically 0, we can say thatStrawberry sells the most.E. Since the p-value is basically 0, we can say thatflavor does effect the average sale of these


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