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Unformatted text preview: Engineering Statistics ENGRD270 Homework 2: Descriptive Statistics (contd) Spring 2008 Hand in by 1pm on Fri, Feb 8 in the ENGRD270 dropbox (between 2nd floor Rhodes and 3rd floor Upson). Be sure to write your name and section number (1–6) or day&time on your homework. 1. The “handy” formula for the sample correlation coefficient. For a sample of pairs ( X 1 ,Y 1 ) ,..., ( X n ,Y n ), show the alternate formula r = [ X X i Y i- n X · Y ] / [( n- 1) S X S Y ] . Here S 2 X = [ ∑ X 2 i- n X 2 ] / ( n- 1) and similarly S 2 Y . [ Hint: Study the “computing formula” for the sample variance in Devore 7e, page 34.] 2. In an experiment, two types of .45 caliber bullets (230 grain and 200 grain) were fired several times into oak wood from a distance of 15 feet. The penetration depths (in mm.) for each firing can be found the following table: 230 grain 40.5 38.3 56.0 42.5 38.3 27.8 200 grain 63.8 64.6 59.5 60.7 58.0 59.1 55.8 54.6 The first row represents the penetration depths of six firings of the 230 grain bullets and the second row of eight firings of the 200 grain bullets....
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This homework help was uploaded on 02/13/2008 for the course ENGRD 2700 taught by Professor Staff during the Spring '05 term at Cornell.
- Spring '05