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The director of admissions at the University of Maryland, University College is

ID: 3174831 • Letter: T

Question

The director of admissions at the University of Maryland, University College is concerned about the high cost of textbooks for the students each semester. A sample of 25 students enrolled in the university indicates that x(bar) = $515.40 and s = $43.20. Using the .10 level of significance, is there evidence that the population mean is above $300? No, because 500 is below the lower limit of the confidence interval Yes, because 300 is below the lower limit of the confidence interval No, because 300 is in the confidence interval Yes, because 300 is in the confidence Interval

Explanation / Answer

right choice is second. Yes, because 300 is below the lower limit of the confidence interval

here n=25, sample mean=315.4,sd=43.2

(1-alpha)*100% confidence interval for mean=mean± z(alpha/2)*sd/sqrt(n)

90% confidence interval for mean=mean±z(0.1/2)*sd/sqrt(n)=315.4±1.645*43.2/sqrt(25)=315.4±14.2=

=(301.2,329.6)

since 300 is out of the interval , so we can say that there is evidence of population mean is above 300.