Consider independent random samples from two populations that are normal or approximately normal or the case in which both

Question

Consider independent random samples from two populations that are normal or approximately normal or the case in which both sample sizes are at least 30 Then if o and are unknown but we have reason to believe that o we can pool the standard deviations Using sample sizes n and n the sample test statistic x x has a Student s t distribution where 2 with degrees of freedom d f n n 2 and where the pooled standard deviation s is n 1 s 2 n 1 5 n n 2 Note With statistical software select the pooled variance or equal variance options LAUSE SALT a There are many situations in which we want to compare means from populations having standard deviations that are equal This method applies even if the standard deviations are known to be only approximately equal Consider a report regarding average incidence of fox rabies in two regions For region I n 16 x 4 6875 and s 3 0489 and for region II n 15 x 4 and s 2 1381 The two sample standard deviations are sufficiently close that we can assume Use the method of pooled standard deviation to consider the report testing if there is a difference in population mean average incidence of rabies at the 5 level of significance Round your answer to three decimal places State the null and alternate hypotheses Enter for as needed H i th kh ng H M 12 Use the sample test statistic to find the corresponding t value Test the difference Round your final answer to two decimal places

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