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PSY201 11.13.13

# 63 123 7 0 0 0 8 1 1 61 6 1 1 61

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Unformatted text preview: rela7on coeﬃcient)   Abbreviated as li`le r   Interpreta1on   Sign (+ vs  ­) tells you about direc7on   Value tells you about the strength: close to  ­1 or closer to 1 represents a stronger correla7on, closer to 0 represents a weaker correla7on 10 11/13/13   Which is stronger?   0.40 versus 0.45   0.80 versus  ­0.75    ­0.23 versus 0.23   Step 1: Change all scores to Z scores. Figure the mean and SD of each variable, then convert each raw score to a Z score   Step 2: Figure the cross ­product of the Z scores for each person, by mul7ple each person’s Z score from variable 1 by their Z score from variable 2   Step 3: Add up the cross ­products of the Z scores   Step 4: Divide by the number of par1cipants in the study 11 11/13/13 r = ΣZxZy N Sum of the cross ­products of Z scores, divided by the total number of par7cipants in the study (i.e., total “sets” of scores)   Find the correla7on coeﬃcient for the associa7on between number of hours slept and a person’s next day mood Number of hours slept Posi1ve mood 5 2 7 4 8 7 6 2 6 3 10 6 12 11/13/13   Step 1: Change all scores to Z scores Number of hours slept X  ­ M (X – M)2 Z scores (Zx) = (X ­M)/SD 5  ­2 4  ­2/1.63 =  ­1.23 7 0 0 0 8 1 1 .61 6  ­1 1  ­.61 6  ­1 1  ­.61 10 3 9 1.84 Σ = 42 SS = 16 M = 7 SD2 = 16/6 = 2.67 SD = 1.63   Step 1: Change all scores to Z scores Posi1ve mood X  ­ M (X – M)2 Z scores (Zy) = (X ­M)/SD 2  ­2 4  ­2/1.92 =  ­1.04 4 0 0 0 7 3 9 1.56 2  ­2 4  ­1.04 3  ­1 1  ­.52 6 2 4 1.04 Σ = 24 SS = 22 M = 4 SD2 = 22/6 = 3.67 SD = 1.92 13 11/13/13   Step 2: Figure the cross ­product for each set Zx (Hours Slept) Zy (Posi1ve mood) Cross ­Products of Z Scores  ­1.23  ­1.04  ­1.23 *  ­1.04 = 1.28 0 0 0 .61 1.56 0.95  ­.61  ­1.04 0.63  ­.61  ­.52 0.32 1.84...
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