agridat (version 1.16)

lucas.switchback: Switchback trial in dairy with three treatments

Description

Switchback trial in dairy with three treatments

Usage

data("lucas.switchback")

Format

A data frame with 36 observations on the following 5 variables.

cow

cow factor, 12 levels

trt

treatment factor, 3 levels

period

period factor, 3 levels

yield

yield (FCM = fat corrected milk), pounds/day

block

block factor

Details

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.

References

Sanders, WL and Gaynor, PJ. 1987. Analysis of Switchback Data Using Statistical Analysis System. Journal of Dairy Science, 70, 2186-2191. http://doi.org/10.3168/jds.S0022-0302(87)80273-4

Examples

# NOT RUN {
data(lucas.switchback)
dat <- lucas.switchback

# Create a numeric period variable
dat$per <- as.numeric(substring(dat$period,2))

require(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 diffs

# }