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# exam 1 answers - 59 97 45000 − =.7115 s y = 1 7 70000 −...

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Psychology 2801 Answers to the Practice Problems 1) A psychologist obtained the following set of data: 3, 8, 13, 23, 26, 26, 26, 27, 28, 28, 29, 30, 32, 41, 49, 56 a) Calculate the mean, median, and mode for these data. Mean = (445) / 16 = 27.8125 Median = (27 + 28) / 2 = 27.5 Mode = 26 b) Calculate the range, variance, and standard deviation for these data. Range = 56 -3 = 53 Variance = s 2 = (2702.438) / (16 – 1) = 180.1625 s = 1625 . 180 2 = s = 13.422 2) An employee at a testing service wants to know whether scores on the SAT verbal section are correlated with scores on the SAT math section. Compute Pearson’s r for these data: SAT Verbal (x - x ) SAT Math (y - y ) Cross-product 350 -107.143 350 -150 16071.45 350 -107.143 500 0 0 400 -57.143 400 -100 5714.3 450 -7.143 450 -50 357.15 500 42.857 650 150 6428.55 550 92.857 600 100 9285.7 600 142.857 550 50 7142.85 45000 70000 ) ( 500 86 . 57142 ) ( 143 . 457 2 2 = Σ = Σ = = Σ = y y y x x x s x = 1 7 86 . 57142 =97.59 r = ) 1 7 ( * 012 . 108 *

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Unformatted text preview: 59 . 97 45000 − = .7115 s y = 1 7 70000 − =108.012 The correlation between the two variables equaled .7115. 3) A developmental psychologist wants to know if IQ can be predicted using birth weight. She randomly samples seven psychology majors at her university and gives them an IQ test. Next, she obtains the birth weight of the students from their hospitals (with permission, of course!). a) Obtain the regression equation for these data. b) Predict IQ using birth weight scores of 4.8 and 6.9. Birth Weight (lbs.) IQ 5.8 122 6.5 120 8.0 129 5.9 112 8.5 127 7.2 116 9.0 130 271 . 7 = x 286 . 122 = y s x = 1.270 s y = 6.8 r = ) 1 7 ( * 7 * 270 . 1 757 . 40 − = .787 [ ] 787 . 27 . 1 8 . 6 1 = b = 4.214 ) 271 . 7 * 214 . 4 ( 286 . 122 − = b = 91.646 ) ( 214 . 4 646 . 91 ˆ x y + = b . ) 8 . 4 ( 214 . 4 646 . 91 ˆ + = y = 111.873 ) 9 . 6 ( 214 . 4 646 . 91 ˆ + = y = 120.723...
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exam 1 answers - 59 97 45000 − =.7115 s y = 1 7 70000 −...

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