This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: 36226 Summer 2010Homework 2Due July 61. Descriptive statistics.For this problem you will need the data filegdpdata.Rdataavailable on the website. Toload the data file, useload(‘/path/to/datafile/gdpdata.Rdata’).Once loaded, sayattach(data). It contains 181 rows and four variables:•country—the name of each of the 181 countries•gdp—total GDP for 2008 or 2009 (depending on the most recent estimate)•gdppc—GDP per capita•labs—a code number classifying each country into one of 7 groups:1= Eastern Europe,2= South America, Central America, and Mexico,3= Western Europe, US, Canada,Japan, Australia, New Zealand, and Israel,4= Middle East,5= Asia,6= Africa,7=Various small island nations.(a) Make a histogram of GDP and supplement it with descriptive statistics using the functionshist()andsummary().(b) Describe the shape of the distribution. What is the center and spread? Are there anyoutliers?(c) It seems like statisticians are obsessed with the normal distribution. One of the reasons for that is that many inferential methods have the assumption that the data follows a normal distribution. When data is heavily skewed, it is therefore sometimesdesirable to “fix” it so that it is more “normal like” using a transformation. In particular, when data is right skewed, this can be done using transformations of the formx1/2,x1/3,x1/4,...,log(x). Find a transformation that will “make the data approximately normal”, create a histogram of the transformed data, and fit a normal distribution to it. To fit a normal distribution, find the mean and sd of the transformed data....
View
Full
Document
This document was uploaded on 07/14/2011.
 Summer '09
 Statistics

Click to edit the document details