L1 chapter 7 new(1)

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Unformatted text preview: x µ= i 900 = 990 • Population Standard Deviation σ= ∑ (x i − µ )2 900 = 80 – Applicants Wanting On-Campus Housing • Population Proportion 648 p= = .72 900 ECO 3411 17 Example: UCF • Take a Sample of 30Applicants Using a Random Number Table We will need 3-digit random numbers to randomly select applicants numbered from 1 to 900. We will use the last three digits of the 5-digit random numbers in the third column of a random number table. The numbers we draw will be the numbers of the applicants we will sample unless • the random number is greater than 900 or • the random number has already been used. We will continue to draw random numbers until we have selected 30 applicants for our sample. ECO 3411 18 Example: UCF • Use of Random Numbers for Sampling 3-Digit Random Number 744 436 865 790 835 902 190 436 etc. Applicant Included in Sample No. 744 No. 436 No. 865 No. 790 No. 835 Number exceeds 900 No. 190 Number already used etc. ECO 3411 19 Example: UCF • Sample Data Random No. Number 1 744 2 436 3 865 4 790 5 835 . . 30 685 Applicant SAT Score On-Campus Connie Reyman 1025 Yes William Fox 950 Yes Fabian Avante 1090 No Eric Paxton 1120 Yes Winona Wheeler 1015 No . . . Kevin Cossack 965 No ECO 3411 20 Example: UCF • Take a Sample of 30 Applicants Using ComputerGenerated Random Numbers – Excel provides a function for generating random numbers in its worksheet. – 900 random numbers are generated, one for each applicant in the population. – Then we choose the 30 applicants corresponding to the 30 smallest random numbers as our sample. – Each of the 900 applicants have the same probability of being included. ECO 3411 21 Using Excel to Select a Simple Random Sample • Formula Worksheet A 1 2 3 4 5 6 7 8 9 B C Applicant Number 1 2 3 4 5 6 7 8 SAT S core 1008 1025 952 1090 1127 1015 965 1161 On-Campus Housing Yes No Yes Yes Yes No Yes No D Random Number =RAND() =RAND() =RAND() =RAND() =RAND() =RAND() =RAND() =RAND() Note: Rows 10­901 are not shown. ECO 3411 22 Using Excel to Select a Simple Random Sample s Value Worksheet A 1 2 3 4 5 6 7 8 9 B C D Applicant Number 1 2 3 4 5 6 7 8 SAT Score 1008 1025 952 1090 1127 1015 965 1161 On-Campus Housing Yes No Yes Yes Yes No Yes No Random Number 0.41327 0.79...
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This note was uploaded on 01/17/2014 for the course ECO 3411 taught by Professor Staff during the Winter '08 term at University of Central Florida.

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