# ECON 15A Study Guide - Midterm Guide: Trail Of Broken Treaties, Scatter Plot, Standard DeviationExam

by OC2657751

Department

EconomicsCourse Code

ECON 15AProfessor

Paul ShireyStudy Guide

MidtermThis

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TEST FOUR

PROBABILITY AND STATISTICS, ECON 15A

NOVEMBER 20, 2015

1. Is it possible for two variables to have a strong association, but the correlation coefficient fails to measure it? Please explain.

2. In a scatter diagram, which points have the greatest say in determining the direction and strength of the association?

3. Is it possible for the covariance to be positive, yet the correlation coefficient is negative? Please explain.

4. Let’s say that the correlation between hours studied and test score is 0.5 for UCI students. Let’s say that the correlation between

hours studied and test score is 0.4 for Cal State Fullerton students. UCI students score higher and study more than Cal State Fullerton

students. For the combined groups, is the correlation for between hours studied and test score most likely to be A) less than 0.4;

B) between 0.4 and 0.5; C) greater than .5. There is no need to explain.

5 – 6. (Two questions – twenty points) There are five people with the below heights and weights. Please calculate the correlation

coefficient. YOU MUST SHOW ALL YOUR WORK

Andy 65 inches 150 pounds

Beth 64 inches 100 pounds

Carl 65 inches 160 pounds

Diane 67 inches 160 pounds

Edgar 69 inches 180 pounds

7. True or false and explain: If the covariance of two variables equals zero, then they are independent.

8. There is a game. If you play it, there is a 50% chance that you will lose $2. There is a 25% chance that you will lose $8. There is a

25% chance that you will win $16. If you play it 25 times, how much do you expect to win (or lose)? Show ALL your work.

9. Let’s continue with the game described in question 8. You play the game 25 times, what is the standard deviation of the amount

won (or lost)? Show ALL your work.

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