Bus 578 Business Statistics

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1Assignment 3Business StatisticsBus 578Spring-2014Ahmed HossainCWID: 50116869Date: 4/6/2014Assignment-3(Chs.9,10and12)Due by Midnight of Sunday,April 6th, 2014: Total75 pointsTrue/False(Onepoint each)Chapter 91.Themanager of the quality department for a tire manufacturing company wants to know theaverage tensile strength of rubber used in making a certain brand of radial tire. The population isnormally distributed and the population standard deviation is known. She uses a Z test to test thenull hypothesis that the mean tensile strength is 800 pounds per square inch. The calculated Ztest statistic is a positive value that leads to a p-value of .009for the test. If the significance level()is .01, the nullhypothesis would be rejected.True2.You cannot make a TypeIIerror when the null hypothesis is true.True

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23.The power of a statistical test is the probability ofnotrejecting the null hypothesis when it istrue.False4.The level of significance indicates the probability of rejecting afalsenull hypothesis.False5. When conducting a hypothesis test about a single mean, other relevant factors held constant,increasing the level of significance from .05 to .10 willdecreasethe probability of a Type IIerror.TrueChapter106.In an experiment involving matched pairs, a sample of 14 pairs of observations is collected.The degree of freedom for the t statistic is 12.False7.In testing the difference between two means from two independent populations, the samplesizesdo nothave to be equal to be able to use the Z statistic.True8.In testing the difference between the means of two independent populations, ifneitherpopulation is normally distributed, then the sampling distribution of the difference in means willbe approximately normal provided that the sum of the sample sizes obtained from the twopopulations is at least 30.True9.If the limits of the confidence interval of the difference between the means of two normallydistributed populations were 0.5 and 2.5 at the 95% confidence level, then we can conclude thatwe are 95% certain that there isnosignificant difference between the two population means.False10.When comparing two population means based on independent random samples, the pooledestimateof the variance is used if thepopulation standard deviations arenotknownand assumedunequal.FalseChapter 1211.The chi-square distribution is a continuous probability distribution that isalwaysskewed totheright.True12.In a contingency table, when all the expected frequencies equal the observed frequencies thecalculated2statistic equals1.False13.In a contingency table, if all of the expected frequencies equal the observed frequencies, thenwe can conclude that there is a perfect dependence between rows and columns.False14.In performing a chi-square test of independence, as the difference between the respectiveobserved and expected frequencies decrease, the probability of concluding that the row variableis independent of the column variable increases.True

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315.When we carry out a chi-square test of independence, the expected frequencies are based ontheNullhypothesis.TrueMultiple Choices(Twopoints each)Chapter 91.If a null hypothesis is rejected at a significance level of .05,it will ______ berejected at asignificance level of .01A.AlwaysB.SometimesC.Never2. If a null hypothesis is not rejected at a significance level of .10, it will ______ be rejected at asignificance level of .05A.AlwaysB.SometimesC.Never3.Whencarrying out a large sample test of H0:=10 vs. Ha:10 by using a p-value, wereject H0at level of significancewhen the p-value is:A.Greater than/2B.Greater thanC.Less thanD.Less than/2E.Less than Z4. If you live inCalifornia, the decision to buy earthquake insurance is an important one. Asurvey revealed that only 119of 340randomly selected residences in one CaliforniaCountywere protected by earthquake insurance.Calculate the appropriate test statistic to test the hypotheses that 40%or morebuy the insurance.(You are dealing with proportions which are small numbers. Therefore keep at least four decimalplaces in your intermediate steps and do the rounding to the two decimal places at the end only).A.1.88B.1.93C.-1.88D.-1.93E.-1.65Chapter 105.In order to test the effectiveness of a drug called XZR designed to reduce cholesterol levels,20 heart patients' cholesterol levels are measured before they are given the drug. The same 20

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