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Course Documents

Chapter 1 - Intro

Chapter 2 - Methods for Describing Sets of Data

Chapter 3 - Probability

Chapter 4 - Discrete Random Variables

Chapter 5 - Normal Random Variables

Chapter 6 - Sampling Distributions

Chapter 7 - Confidence Intervals

Chapter 8 - Tests of Hypothesis: One Sample

Chapter 9 - Confidence Intervals and Hypothesis Tests: Two Samples

Sample Exam I: Chapters 1 & 2

Sample Exam II: Chapters 3 & 4

Sample Exam III: Chapters 5 & 6

Sample Exam IV: Chapters 7 & 8

Ask the Professor Forum

I don't know if I don't understand it or its just that I've been all day doing problems, but I don't know how to do D. Can you help me please?? :)

I plugged an entire class of 200 into SPSS in order to calculate the least squares line for the entire data set. The results were as follows: y^ = 0.512 x + 70.196 .

a) What does x = 0 represent here?
b) What is the expected grade for students who do not earn any clicker points?
c) What is the average grade for a student who has 20 clicker points?
d) I pulled the grade and clicker points for a randomly chosen student from a different class of statistics from the spring term 2010. That student had 35 clicker points and a 94% in the class. Plug 35 points into our model, and determine the prediction error for this case.

Posted to STATS 2 on Thursday, August 15, 2013   Replies: 2

Professor Mcguckian
4:35 PM EST

Hi Eric,
We have to compare, by subtraction, what the actual grade for the student who had 35 points was and what the model predicts for students with x = 35 points.

First plug 35 into the model: 0.512*35 +70.196 = 88.116   This means the model says students on average will have an 88.116% when they earn 35 points.  In reality, the student we pulled from the grade book had a 94%, so the prediction error is y - y-hat = 94 -88.116 = 5.884

Professor McGuckian

3:32 PM EST
Thank you professor! This was the same problem I was having and your explanation really cleared things up for me!

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