Homework 10 (20 points) - due 05/31/00

Rweb

Problem 1:
Recall the exercise we tried in class in Lecture 10 (05/23). We used the student data available on http://www.math.usu.edu/~vukasino/teaching/spring2000/complab/student_data1.prn and used the JavaScript version of Rweb to obtained summary statistics for the variables Age and Siblings. Now try yourself to calculate a few more summary statistics such as the median and the variance of Height and Weight. First make sure to identify the appropriate columns of the matrix X that represent these two variables. Can you also calculate the correlation between these two variables and draw a scatterplot of Height (horizontal) vs. Weight (vertical)?

Problem 2:
Also, recall how we calculated simple linear regression of Siblings on Age. Now try yourself to calculate a simple linear regression where Weight is the response and Age is the predictor variable. The required syntax is result <- lm(response ~ predictor). Here, result <- means that we assign the outcome of the calculation right of <- to a new variable called result. lm represents a function that calculates a linear model. response ~ predictor represents the expression that should be calculated. You have to replace response and predictor with the appropriate columns of the matrix X. Finally, you have to produce some visible output using the command summary(result).

Rice Virtual Lab in Statistics - Data Analysis

Homework problems

Using Rice's Data Analysis Lab Package, solve the problems listed below. Describe exactly all steps needed to obtain the required results (including data editing/recoding). If you encounter any problem (e.g., if a certain applet is not working or if you can clearly see that the results are wrong) mention this explicitely in your written report.

• Obtain summary statistics for "Height" and "Weight". Also obtain possible graphical displays for these variables.
• Perform a regression analysis of weight on age. What is the predictor variable? What is the dependent variable?
• Does color of eyes (variable "Eyecolor") have significant influence on weight? Answer this question by carrying out an ANOVA analysis.

Webstat

Using the data set on Labor force available as a sample data set in the site:

• provide a brief statement on what the data set is measuring.
• analyze for differences between 1968 and 1972 in the measured variable (hint: a paired t-test would probably be useful here).
• report summary statistics and results of analysis.
• produce whichever graphics you think will best display the data

Statlets

Homework Problem: Open Statlets, load the data. After speaking to the person who put down that they were 8'7" we found out that they actually wrote 5'7" but the 5 looked like an 8. Find this outlier in the data in the Statlets data screen and change 103.0" to 67.0". What is the 95% confidence interval? Then do a t-test on H_o: m = 68". Do we reject at 5%? Give another reason why you know this to be the case. For what value of m would we not reject at 5%?

XploRe

Homework:

1. Write a program to plot the histogram and boxplot for sibling and weight, respectively.

2. Write a program to perform the regression analysis and plot the regression line of Weight on height.