2100 many middle schools have initiated a program

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(2.100) Many middle schools have initiated a program that provides every stu-dent with a free laptop computer. Student usage of laptops at a middleschool that participates in the initiative was investigated inAmericanSecondary Education(Fall 2009). In a sample of 106 students, the re-searchers reported the following statistics on how many minutes perday each student used his or her laptop for taking notes:¯x= 13.2,s= 19.5.(a) Compute the interval, ¯x±2s.(b) Explain why the distribution of laptop usage for taking notes forthese 106 students cannot be symmetric.(c) Given your answer to part (b), what percentage of the 106 studentshave laptop usages that fall within the ¯x±2sinterval?(2.118) University of Hawaii language professors C. Hitosugi and R. Day incor-porated a 10-week extensive reading program into a second-semesterJapanese language course in an effort to improve students’ Japanesereading comprehension (Reading in a Foreign Language, April, 2004).The professors collected 266 books originally written for Japanese chil-dren and required their students to read at least 40 of them as part of2
the grade in the course. The books were categorized into reading levels(colour coded for easy selection) according to length and complexity.Fourteen students participated in the program. The number of booksactually read by each student and the student’s grade in the course arelisted in the table below.GradesABC53424040282122# of books39343420163024(a) Find the mean and standard deviation of the number of booksread by students who earned an A grade. Find thez-score for anA student who read 40 books. Interpret the result.(b) Find the mean and standard deviation of the number of booksread by students who earned either a B or a C grade. Find thez-score for a B or C student who read 40 books.Interpret theresult.(c) Refer to parts (a) and (b). Which of the two groups of studentsis more likely to have read 40 books? Explain.(2.136) Tills are glacial drifts consisting of a mixture of clay, sand, gravel, andboulders. Engineers from the University of Washington’s Departmentof Earth and Space Sciences studied the chemical makeup of buried tillsin order to estimate the age of the glacial drifts in Wisconsin (AmericanJournal of Science, January, 2005). The ratio of the elements aluminum(AI) and beryllium (Be) in sediment is related to the duration of burial.The AI–Be ratios for a sample of 26 buried till specimens are given inthe accompanying table and saved in theTILLRATIOfile.3.754.053.813.233.133.303.213.324.093.905.063.853.884.064.563.603.274.093.383.372.732.952.252.732.553.06(a) Find and interpret thez-score associated with the largest ratio,the smallest ratio, and the mean ratio.

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Term
Summer
Professor
Dr.JoseCorrea
Tags
Statistics, REM, previous sleep stage, current sleep stage

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