HW+2 - The correct choice gets 4 points while one point is...

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STAT 20: Lecture Section 2. Spring 2011 Homework #2 Hand in HW to your GSI at the START of Section on Thursday Feb 24 th . Make sure to put your name, SID, section number, your GSI’s name and section time on the first page. Please staple all the pages together. This homework has six Questions in total. 1. Text Page 106 Q7 [Add (c): calculate the SD ( use the method given in lecture )] 2. Text Page 135 Q2 3. Text Page 135 Q3 4. For a large group of ten year old boys the correlation between height and weight is 0.4 with a football shaped scatter diagram. Predict the percentile for weight of a boy in this group who is at the 75 th percentile of heights. Assume that for this group both heights and weights follow normal curves. 5. A multiple choice quiz has 10 questions each with 5 options.
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Unformatted text preview: The correct choice gets 4 points while one point is subtracted for every incorrect choice. The possible scores range from -10 to 40. A scatter plot is obtained for 200 students (all of whom attempt every one of the 10 questions) showing the number of questions a student got right versus their total score on the quiz. What is the correlation? 6. The exponential density with parameter λ has pdf f(x) given by: f(x) = e-x :for x ≥ 0 with f(x) = 0 otherwise. (i) Work out the cdf F(x) = ( ) x f u du-∞ ∫ as a function of x and . (ii) Find the median of the distribution as a function of . (iii) Sketch the pdf and cdf and indicate what the median says on both....
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