amylase {nparLD} | R Documentation |
Measurements of alpha-amylase levels (in U/ml) of the saliva from a group of volunteers.
data(amylase)
Longitudinal data of 14 probands with alpha-amylase level measurements taken on 8 occasions (4 times per day for 2 days).
In clinical chemistry, it is important for the determination of reference intervals to investigate whether a variable of interest has a circadian rhythm. If so, the reference intervals cannot be determined independently of time. This question is to be analyzed in the case of alpha-amylase in saliva. Measurements of alpha-amylase levels were taken from the saliva of 14 volunteers, four times per day (8 a.m., 12 p.m., 5 p.m., 9 p.m.) on two days (Monday (m), Thursday (t)), since differences in the alpha-amylase profiles immediately after a weekend as opposed to the middle of the week are suspected. Thus, each subject was examined on Monday and Thursday.
Brunner, E., Domhof, S., and Langer, F. (2002). Nonparametric Analysis of Longitudinal Data in Factorial Experiments,
Wiley, New York.
Brunner, E. and Langer, F. (1999). Nichtparametrische Analyse longitudinaler Daten, R. Oldenbourg Verlag, Munchen Wien.
## Analysis using LD-F2 design ## data(amylase) var<-c(amylase[,"m8"],amylase[,"m12"],amylase[,"m17"],amylase[,"m21"], amylase[,"t8"],amylase[,"t12"],amylase[,"t17"],amylase[,"t21"]) time1<-factor(c(rep("M",56),rep("T",56))) time2<-c(rep(8,14),rep(12,14),rep(17,14),rep(21,14), rep(8,14),rep(12,14),rep(17,14),rep(21,14)) subject<-c(rep(amylase[,"Proband"],8)) ex.f2<-ld.f2(var=var,time1=time1,time2=time2,subject=subject, time1.name="Day",time2.name="Time",description=FALSE) ## Wald-type statistic ex.f2$Wald.test # Statistic df p-value #Time 0.6761043 1 4.109314e-01 #Day 35.8647640 3 7.997949e-08 #Time:Day 14.3020921 3 2.521503e-03 ## ANOVA-type statistic ex.f2$ANOVA.test # Statistic df p-value #Time 0.6761043 1.000000 4.109334e-01 #Day 14.2671950 2.858344 5.883893e-09 #Time:Day 5.2242782 2.184249 4.151609e-03