{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}


statsexam1f11sol - Economic Statistics Exam 1 Last name...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Economic Statistics Exam 1 Last name: September 22, 2011 First name: Class time: 11:00-12:15 or 12:30-1:45 PID: Please sign that you abide by the honor pledge: This exam contains twelve short answer questions (worth 6 points each) and three long answer questions (worth 10 points each). Please answer in the space provided. In all problems where you need to make a calculation, simplify your answer as much as possible. Technique is important, so show your work clearly. Short Questions (6 points apiece) 1. What is the approximate relationship between the range and standard deviation of a variable? The standard deviation is approximately ¼ of the range. 2. The variable X comes from a distribution with a mean of 29 and a variance of 4 . If Mr. Smith’s value of X equals 34, then his standardized value is what? The standardized value is calculated as z = ( x x )/ s x . Note that s x = s x 2 = 4 = 2 . In this case, the answer is z = (34 29)/2 = 2.5 . 3. What does it mean for events A and B to be “statistically independent”, and what does it mean for them to be “mutually exclusive”? Two events are statistically independent if knowing the outcome of one does not cause us to revise our expectations about the likeliness of the other; P [ A | B ] = P [ A ] . Two events are mutually exclusive if they cannot both occur simultaneously; P [ A and B ] = 0 . 4. What is the rule of thumb for determining whether the correlation between two variables is a “meaningful relationship” or due to chance?
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}