Test 3 - Solutions A-C.docx

# A the slope tells us how much y changes when x

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9. A – The slope tells us how much Y changes when X increases by one. 10. B – The intercept tells us what Y would be if X were equal to zero. 11. E – It is something other than the two variables being studied that affects the relationship. 12. C – On the scatterplot, we can see that the original data for magnitude of the earthquake ranges from about 1.5 to 7.5. The value of a magnitude 10.0 earthquake would be far outside the range of the data, so making a prediction for X = 10.0 would be extrapolation. 13. B – The 3 conditional distributions are significantly different, so there is a relationship between the two variables. 14. D – The reversal of the relationship between two categorical variables is Simpson’s paradox. 15. F – The closer r is to –1 or 1, the stronger the relationship. 16. A – The closer r is to 0, the weaker the relationship. 17. S xx = ∑ x 2 n x 2 = 701 – ( 53 ) 2 5 = 701 – 561.8 = 139.2 S yy = ∑ y 2 n y 2 = 849 – ( 59 ) 2 5 = 849 – 696.2 = 152.8 S xy = ∑ xy –  n y x = 506 – ( 53 ) ( 59 ) 5 = 506 – 625.4 = –119.4 r = xy xx yy S S S = 119.4 ( 139.2 )( 152.8 ) = –0.8187
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• Spring '15
• Stat Test 3 Solutions

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