# 2_23_09 - Selected slides Key idea#2 the sum(difference of...

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Selected slides 2-23-09

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2 Key idea #2 – the sum (difference) of two normal r.v.’s ( 29 ( 29 . , ~ and , ~ 2 2 2 1 1 1 σ μ σ μ N X N X Let t then independen are and If 2 1 X X . , ~ 2 2 2 1 2 1 2 1 2 1 2 1 + = + = + + + σ σ σ μ μ μ X X X X N X X The sum (difference) of two independent normal R.V.s is normal with: mean = sum (difference) of individual means variance = sum of individual variances. . , ~ 2 2 2 1 2 1 2 1 2 1 2 1 + = - = - - - σ σ σ μ μ μ X X X X N X X
Can we use the Z-distribution for our analysis? A. Check that all 4 Binomial criteria apply for each population: 1. n = Fixed number of trials for Population 1 m = Fixed number of trials for Population 2 1. Each sample has independent trials and samples are taken
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Unformatted text preview: independently from one another. 2. Outcome for each trial of each sample is: ‘success’ or ‘failure’. Success for trials of sample 1 = …. Failure =….… Success for trials of sample 2 = …. Failure =……. 4. Population proportion of successes corresponding to each sample remains constant from trial to trial. ( 29 ( 29 10 ˆ 1 and 10 ˆ 10 ˆ 1 and 10 ˆ ≥-≥ ≥-≥ q m q m p n p n B. Check that each sample proportion distribution may be approximated as normal....
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• Spring '09
• GELLAR

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