Exam 1 solutions

# Exam 1 solutions - Boston University Department of...

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Boston University Department of Biomedical Engineering ENG BE200: Introduction to Probability Fall 2010 Exam 1 Show ALL the steps in your calculations including the equations. Problem 1 [40 pts] a) [ 5 ] b) M x = 15/4 = 3.75 [ 10 ] M y = 25/4 = 6.25 S x 2 = ( x i M x ) 2 i = 1 4 4 1 = 6.25 S x = 2.5 S y 2 = ( y i M y ) 2 i = 1 4 4 1 = 10.917 S y = 3.304 c) r xy = S xy /( S x * S y ) [ 10 ] = ( x i M x )( y i M y ) i = 1 4 (4 1)* S x * S y = 23.25 / ( 3 * 2.5 * 3.304 ) 0 2 4 6 8 10 12 0 2 4 6 8 Y X Scatterplot Scatterplot

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= 0.938 The data does indicate a strong correlation between the x values and y values however this doe not tell us that there is a causal relationship between these two variables. It is impossible to say if x causes y or y causes x given the data. The value of r 2 is a measure of the fit of the data to the line of best fit. The closer the value is to one the better the fit of the data to the line. Alternatively 1- r 2 represents the
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## This note was uploaded on 10/19/2010 for the course BE 200 taught by Professor Ddd during the Fall '09 term at BC.

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Exam 1 solutions - Boston University Department of...

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