Statistical Software Packages

STAT 362 / IT 362: Introduction to Computer Statistical Packages

Spring, 2007

Monday and Wednesday, 4:30 pm - 5:45 pm. Science and Technology I, room 122

TA: Ruihua Xu
Office hours: Mondays 6:00pm--7:00pm; Fridays 10:00am--11:00am.
Room 146, Science & Technology II.

If you send email to the instructor or to the TA , please put "Stat 362" or "IT 362" in the subject line.

This web page and the links to notes will evolve as the semester progresses. In particular, links to solutions to assignments and quizzes will be posted at appropriate times (after the fact, of course!).

The general description of the course is available at www.scs.gmu.edu/~jgentle/stat362/

The references below refer to

Ronald P. Cody and Jeffrey K. Smith (2006), Applied Statistics and the SAS Programming Language, Fifth Edition, Pearson Prentice Hall, Upper Saddle River, NJ.
Lora D. Delwiche and Susan J. Slaughter (2003), The Little SAS Book, Third Edition, SAS Institute Inc., Cary, NC.

Note the websites for the books, where sample programs and datasets are available:

The final exam is May 9 at 4:30.

Week 1: Jan 22, 24

Computer systems and organization; applications software.
Data organization for statistical analysis.
The "standard" rectangular array
- Observations; rows ("cases", "instances", "records", etc.)
- Variables; columns ("features", "attributes", "fields", etc.)
Introduction to the SAS software system
References: Applied Statistics , Chapter 1, and The Little SAS Book , Chapter 1.
- Starting SAS
- The SAS DATA step
- Defining variables and entering data
- Types of data; numeric data, character data
- Creating new variables; the assignment statement
- Simple SAS PROCs: PRINT, MEANS, FREQ, CORR, and SORT
Assignment 1: Exercises 1.2, 1.4, and 1.8 in Applied Statistics (due Monday Jan 29).
Solution

Week 2: Jan 29, 31

More on the SAS DATA step
- Missing values
- More on the INPUT statement
- Input from an ASCII data file (Reference: The Little SAS Book , Chapter 2).
- DROP/KEEP
- Input from another SAS dataset; the SET statement
- Conditional execution (reference: The Little SAS Book , Sections 3.4 and 3.5)
Review of basic statistics (Reference: Applied Statistics , Chapter 2.)
- Descriptive statistics
- Populations and parameters; Samples and statistics:
- Statistical inference
  - Hypothesis testing (t tests); one-sided tests, two-sided tests
  - Estimation: confidence intervals
- qq plots
More about PROCs
- PROC SORT (reference: The Little SAS Book , Section 4.3).
  - Sortkeys
  - The BY statement
- The WHERE statement (reference: The Little SAS Book , pages 102, 103, 306, and 307)
- PROC MEANS and PROC UNIVARIATE (reference: The Little SAS Book , Sections 4.9, 8.1, and 8.2).
  - SAS statements
  - t tests in SAS
Assignment 2: Exercises 2.2, 2.4, and 2.8 in Applied Statistics (due Monday Feb 5).
Solution

Week 3: Feb 5, 7

More on SAS datasets (reference: The Little SAS Book , Sections 2.19-2.22 and Sections 3.1-3.3).
- External files
- Saving and reusing SAS datasets
- Additional statements in the SAS DATA step:
  - SAS functions (reference: Applied Statistics , Chapters 17)
    - Simple functions (SQRT, LOG, RANUNI, etc.)
    - Functions to compute statistics within observations
  - LABEL, FORMAT
  - OUTPUT/DELETE, DROP/KEEP, RENAME
- Multiple datasets within one DATA step
- Working with subsets of a dataset; OBS, FIRSTOBS
Making programs work correctly; reading assignment: The Little SAS Book , Chapter 10
Assignment 3 (due Monday Feb 12).
Solution

Week 4: Feb 12, 14

Graphs for understanding data
Graphs in SAS
Wednesday, Feb 14: Class canceled due to weather.
Assignment 4: Exercises 2.10 and 2.12 in Applied Statistics (due Monday Feb 19).
Solution

Week 5: Feb 19, 21

Monday, Feb 19
- Combining and manipulating SAS datasets (reference: The Little SAS Book , Chapter 6).
  Concatenation, interleaving, merging, updating.
- Quiz 1 (50 minutes; material through week 4).
  Here's a sample from a previous year. Of course yours will be different!! (There may also be some slight differences in coverage this semester.)
Wednesday, Feb 21
- Review of Quiz 1. Version a . Version b . Version c .
- More on concatenation, interleaving, merging, amd updating of SAS datasets.
- PROC FORMAT; custom formats, recoding
  (references: The Little SAS Book , Section 4.7, and Applied Statistics , Chapter 3).
- Still more on the DATA step
  (reference: The Little SAS Book , Chapters 2, 3, and 4).
  - Lagged variables
  - Automatic variables
  - Arrays (reference: Applied Statistics , Chapters 15)
  - DO loops (reference: Applied Statistics , page 419)
  - Labels
  - More on the INPUT statement and controlling output
  - Character data
  - PUT and FILE statements
Assignment 5 (due Monday Feb 26).
Solution

Week 6: Feb 26, 28

Categorical data (Reference: Applied Statistics , Chapter 3.)
The Output Delivery System (reference: The Little SAS Book , Chapter 5).
Assignment 6 lagged variables, loops, etc., and Exercises 3.3, 3.6, and 3.7 in Applied Statistics (due Monday Mar 5).
Solution

Week 7: Mar 5, 7

More on the analysis of categorical data; interpretation of SAS output. (Reference: Applied Statistics , Chapter 3.)
- Are two categorical variables related (or are they "independent")? Chi-squared.
- Unmatched case-control studies. Chi-squared and odds ratio.
- Matched case-control studies. McNemar test.
- Agreement. Kappa.
- Linear trend. Mantel-Haenszel chi-squared.
Assignment 7: Exercises 3.9, 3.10, 3.11, and 3.15 in Applied Statistics (due Monday Mar 19).
Solution

No class Mar 12, 14; GMU Spring Break

Week 8: Mar 19, 21

Review: manipulations of SAS datasets in the DATA step; PROC FORMAT; categorical data.
Wednesday, Mar 21 Quiz 2

Week 9: Mar 26, 28

Review of Quiz 2. Version a . Version b . Version c . Version d . Version e .
Correlation and regression
Correlation and regression
- Correlation
- Simple regression models
- Basic model fitting
- AOV table and F test
- Coefficient estimates and t tests
Regression in SAS (reference: The Little SAS Book , Sections 8.5 and 8.6).
- PROC REG statements
  - MODEL statement
  - P option
  - BY statement
  - PLOT statement
  - P. and R. keywords
  - OVERLAY option
- Output of PROC REG
Assignment 8
SAS program.

Week 10: Apr 2, 4

(Reference: Applied Statistics , Chapter 5)

More on correlation and regression analysis
Measuring variation and co-variation
More on regression analysis
- Inspection of residuals -- patterns; polynomial regression
- Confidence intervals; prediction intervals
- Regression fitting
- Adequacy of fit: R-squared
Assignment 9: Exercises 5.1, 5.5, 5.7, 5.9, and 5.10 in Applied Statistics (due Monday Apr 9).
SAS program.

Week 11: Apr 9, 11

(Reference: Applied Statistics , Chapter 9)

More on multiple linear regression
- Regression model building
- Adequacy of fit: R-squared, adjusted R-squared
- Selection of variables in regression.
Assignment 10 (due Monday Apr 16).
SAS program.

Week 12: Apr 16, 17

(Reference: Applied Statistics , Chapter 9)

Regression models with categorical covariates; "dummy" variables.
Assignment 11: Exercises 9.1 and 9.2 in Applied Statistics (due Monday Apr 23).

Week 13: Apr 23, 25

Monday, Apr 23
- Quiz 3 (regression analysis).
Wednesday, Apr 25
- More on SAS datasets:
  - the pointer in the INPUT statement
  - informats/formats
  - date data (reference: The Little SAS Book , Sections 3.7, 3.8)
  - SQL (reference: The Little SAS Book , Appendix F)
  - importing and exporting SAS datasets (reference: The Little SAS Book , Sections 2.15--2.19)
- SAS macros (reference: The Little SAS Book , Chapter 7, and Applied Statistics , p. 94).
Assignment 12 (due Monday Apr 30).

Week 14: Apr 30, May 2

Statistical data on the web.
More on SAS/GRAPH; Maps.

Exam: May 9, 4:30 - 7:15

The final is comprehensive; it is not limited to material that has appeared on previous quizzes. We have covered a lot of material in this course, and so the exam can only be a sampling of what was covered.