9/26/2016

Quiz 1 Results - Open p:\data\math\hartlaub\elements of statistics\quiz1.R

Assessing Normality

• Should we use the normal model for a given data set?
• 68-95-99.7 Rule
• Normal Quantile Plots - qqnorm in R
• Other Visual Displays

Class Activity on using qqplots to assess Normality

• Open the R script QQPlot.R to conduct simulations that will help you develop your understand of these new plots.
• The script simulates data from normal distributions, uniform distributions, and t distributions. Look at the histograms and qqplots carefully. You can run the commands multiple times to help you distinguish general trends from chance variation.
• Describe each of the plots. Can you explain how the differences in the distributions are appearing on the normal probability plots?
• Use appropriate methods for assessing normality to see if the normal distribution would be an appropriate model for the qunatitative variables from our Data Survey on Day 1.

Class Activity on Sampling Distributions - Open USPennies.R

• Describe the shape of the age distribution for U.S. pennies
• Estimate the mean and standard deviation for this distribution
• Investigate properties of the sampling distribution of the sample average as the sample size increseases.
• General comments about the sampling distribution of a sample average.

Please read Sections 4.1 through 4.3 for class on Wednesday.