Switchback experiment on dairy cattle, milk yield for 3 treatments
Switchback experiment on dairy cattle, milk yield for 3 treatments
data("lucas.switchback")A data frame with 36 observations on the following 5 variables.
cowcow factor, 12 levels
trttreatment factor, 3 levels
periodperiod factor, 3 levels
yieldyield (FCM = fat corrected milk), pounds/day
blockblock factor
Lucas says "because no data from feeding trials employing the present designs are yet available, uniformity data will be used".
Six cows were started together in block 1, then three cows in block 2 and three cows in block 3.
Lucas, HL. 1956. Switchback trials for more than two treatments. Journal of Dairy Science, 39, 146-154. https://doi.org/10.3168/jds.S0022-0302(56)94721-X
Sanders, WL and Gaynor, PJ. 1987. Analysis of Switchback Data Using Statistical Analysis System. Journal of Dairy Science, 70, 2186-2191. https://doi.org/10.3168/jds.S0022-0302(87)80273-4
library(agridat)
data(lucas.switchback)
dat <- lucas.switchback
# Create a numeric period variable
dat$per <- as.numeric(substring(dat$period,2))
libs(lattice)
xyplot(yield ~ period|block, data=dat, group=cow, type=c('l','r'),
auto.key=list(columns=6),
main="lucas.switchback - (actually uniformity data)")
# Need to use 'terms' to preserve the order of the model terms
# Really, cow(block), per:cow(block), period(block)
m1 <- aov(terms(yield ~ block + cow:block + per:cow:block +
period:block + trt, keep.order=TRUE), data=dat)
anova(m1) # Match Sanders & Gaynor table 3
## Analysis of Variance Table
## Df Sum Sq Mean Sq F value Pr(>F)
## block 2 30.93 15.464 55.345 5.132e-05 ***
## block:cow 9 1700.97 188.997 676.426 1.907e-09 ***
## block:cow:per 12 120.47 10.040 35.932 4.137e-05 ***
## block:period 3 14.85 4.950 17.717 0.001194 **
## trt 2 1.58 0.789 2.825 0.126048
## Residuals 7 1.96 0.279
coef(m1) # trtT2 and trtT3 match Sanders table 3 trt diffsPlease choose more modern alternatives, such as Google Chrome or Mozilla Firefox.