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COMM 217
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1Thequartile 1 and quartile 3 monthly sales of a retail storefor athree years periodprior to the implementation of new promotion policy were 15 million and 35 million respectively After the policy was implemented quartile 1 and quartile 3 sales were 25 and 35 million respectively The accurateaThe new policy had no significant positive impact on average sales whatsoeverbThe policy seems to have made a positive improvement in the average sales cThere is no real difference in average sales forthe two periodsdThe variance of sales for the two periods is identical2 Historically a certain process produced outcomes which have measures that are approximately normal with 25 of the measurements less than a value of 650 and 75 less than 850Minimum and maximum values are 550 and 950 A sample is taken and a relative frequency developed that shows 25have values less than 675 and 75 less than825 Minimum and maximum values are 575 and825 respectively Based on a box plot for the two sets of data which of the following statements is most accurateaThe data support the view that the mean of the sample data is less than the mean of the historical data basebThe variance of the distribution of the current outcomes is less than the variance of the historical data cThere are outliers in the distributionsdThe inner and outer fences of the two distributions are equal to the minimum and maximum values 3 The minimums and maximums for two data set A and B are 100 and 300 for data set A and 50 and 350 for data set B Assume thatfor data setsAandB quartiles 1 are identical and thatquartiles 3 arealsoidentical for the data sets A and BThe processgenerating the two distributions are not believed to be normalaIt follows that the variances areequal for both A and BbThe means of the two data sets areequalcIt is not reasonable to assume thatABdTherecanbenooutliersinthedatasetsAandB4 Under certain circumstances the Box plot can be usedto aDescribe the precise shape and peakednessof the distribution of a data setbIndicate the exact numerical degree of skewness cIndicate the location of the mass of the data within the range for the data dDetermine the variances of the data sets5 The Box Plot can be applied to any numerical data set toaTo assist in determining whether there are outliers in the databTo provide the final rules forremoving an outliers from the data cTo create inner and outer fencesaround the mean of the data dTo avoid using the range as an indicator of variationTHE SAMPLE SIZE DETERMINATION AND IMPLICATIONSThe deriving sample size is more than just the application of a formulaMany questions on sample size require an in depth understanding of the concepts involved Start from the fundamentalunderstanding That sampling producesa sampling spacefilled with many different sample of the same size n That each sample will produce a sample mean that differs from the population mean Thus since sampling produces sample estimateswhich differ from the true parameter sampling producessampling errorsSampling errors are therefore inherent to the process and are unavoidableA measure of the sampling error with respect to the estimation of the population mean is XmiN NnnIn any sample space there may besuch errors corresponding to the number of all possible sampleswhere N is the size of the population and nis the sample sizeThese errors represent distances of the sample means from the true population meanfor some distribution of distributionnormal t etc When we know the probability distribution of the sample mean we can derive the probability that an error of a certain size will occurWhile we cannot control sampling errors we can tell the relative frequency certain size errors resulting from the sampling process will occur
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