[R] Learning to do randomized block design analysis

From: Zembower, Kevin <kzembowe_at_jhuccp.org>
Date: Tue, 4 Dec 2007 15:15:07 -0500


We just studied randomized block design analysis in my statistics class, and I'm trying to learn how to do them in R. I'm trying to duplicate a case study example from my textbook [1]:

> # Case Study 13.2.1, page 778
> cd <- c(8, 11, 9, 16, 24)
> dp <- c(2, 1, 12, 11, 19)
> lm <- c(-2, 0, 6, 2, 11)
> table <- data.frame(Block=LETTERS[1:5], "Score changes"=c(cd, dp,
lm), Therapy=rep(c("Contact Desensitisztion", "Demonstration Participation", "Live Modeling"), each=5))
> table

   Block Score.changes                     Therapy
1      A             8     Contact Desensitisztion
2      B            11     Contact Desensitisztion
3      C             9     Contact Desensitisztion
4      D            16     Contact Desensitisztion
5      E            24     Contact Desensitisztion
6      A             2 Demonstration Participation
7      B             1 Demonstration Participation
8      C            12 Demonstration Participation
9      D            11 Demonstration Participation
10     E            19 Demonstration Participation
11     A            -2               Live Modeling
12     B             0               Live Modeling
13     C             6               Live Modeling
14     D             2               Live Modeling
15     E            11               Live Modeling

> model.aov <- aov(Score.changes ~ Therapy + Error(Block), data=table)
> summary(model.aov)

Error: Block

          Df Sum Sq Mean Sq F value Pr(>F)
Residuals  4  438.0   109.5               

Error: Within
          Df Sum Sq Mean Sq F value   Pr(>F)   
Therapy    2 260.93  130.47  15.259 0.001861 **
Residuals  8  68.40    8.55                    
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 

>
I don't understand why R doesn't output a value for F and Pr for the Error (Block) dimension, as my textbook shows 12.807 and 0.0015 respectively. All the other numbers match. Can these two values be recovered? Also, my text shows a total line which R omits. Is this because it's not particularly useful? Thanks for your suggestions and advice. Also, if I'm executing this type of problem in R inefficiently, I'd appreciate suggestions. -Kevin [1] An Introduction to Mathematical Statistics and Its Applications, Larsen and Marx, fourth edition. Kevin Zembower Internet Services Group manager Center for Communication Programs Bloomberg School of Public Health Johns Hopkins University 111 Market Place, Suite 310 Baltimore, Maryland 21202 410-659-6139 ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Received on Tue 04 Dec 2007 - 20:19:05 GMT

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