Description Usage Format Details Source References Examples

Switchback experiment on dairy cattle, milk yield for 4 treatments

1 | ```
data("patterson.switchback")
``` |

A data frame with 36 observations on the following 4 variables.

`y`

response, milk FCM

`trt`

treatment factor, 4 levels

`period`

period factor, 3 levls

`cow`

cow factor, 12 levels

There are three periods. Each cow is assigned to one treatment cycle like T1-T2-T1, where T1 is the treatment in period P1 and P3, and T2 is the treatment in period P2.

There are four treatments.

All 4*3 = 12 treatment cycles are represented.

Data were extracted from Lowry, page 70.

Patterson, H.D. and Lucas, H.L. 1962.
Change-over designs.
*Technical Bulletin 147*, North Carolina Agricultural Experimental Station.

Lowry, S.R. 1989.
Statistical design and analysis of dairy nutrition experiments to
improve detection of milk response differences.
*Proceedings of the Conference on Applied Statistics in Agriculture*, 1989.
https://newprairiepress.org/agstatconference/1989/proceedings/7/

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | ```
## Not run:
library(agridat)
data(patterson.switchback)
dat <- patterson.switchback
# Create groupings for first treatment, second treatment
datp1 <- subset(dat, period=="P1")
datp2 <- subset(dat, period=="P2")
dat$p1trt <- datp1$trt[match(dat$cow, datp1$cow)]
dat$p2trt <- datp2$trt[match(dat$cow, datp2$cow)]
libs(latticeExtra)
useOuterStrips(xyplot(y ~ period|p1trt*p2trt, data=dat,
group=cow, type=c('l','r'),
auto.key=list(columns=5),
main="patterson.switchback",
xlab="First/Third period treatment",
ylab="Second period treatment"))
# Create a numeric period variable
dat$per <- as.numeric(substring(dat$period,2))
# Need to use 'terms' to preserve the order of the model terms
m1 <- aov(terms(y ~ cow + per:cow + period + trt, keep.order=TRUE), data=dat)
anova(m1) # Match table 2 of Lowry
## Analysis of Variance Table
## Df Sum Sq Mean Sq F value Pr(>F)
## cow 11 3466.0 315.091 57.1773 2.258e-06 ***
## cow:per 12 953.5 79.455 14.4182 0.0004017 ***
## period 1 19.7 19.740 3.5821 0.0950382 .
## trt 3 58.3 19.418 3.5237 0.0685092 .
## Residuals 8 44.1 5.511
## End(Not run)
``` |

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