nparLD (version 2.2)

amylase: Alpha-amylase study

Description

Measurements of alpha-amylase levels (in U/ml) of the saliva from a group of volunteers.

Usage

data(amylase)

Format

Longitudinal data of 14 probands with alpha-amylase level measurements taken on 8 occasions (4 times per day for 2 days).

Details

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.

References

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.

Noguchi, K., Gel, Y.R., Brunner, E., and Konietschke, F. (2012). nparLD: An R Software Package for the Nonparametric Analysis of Longitudinal Data in Factorial Experiments. Journal of Statistical Software, 50(12), 1-23.

Examples

## Analysis using LD-F2 design ##
data(amylase)
attach(amylase)
ex.f2<-ld.f2(y=resp, time1=time1, time2=time2, subject=subject,
time1.name="Day", time2.name="Time", description=FALSE)
# LD F2 Model 
# ----------------------- 
# Check that the order of the time1 and time2 levels are correct.
# Time1 level:   M T 
# Time2 level:   8 12 17 21 
# If the order is not correct, specify the correct order in time1.order or 
# time2.order.

## Wald-type statistic 
ex.f2$Wald.test

#          Statistic df      p-value
#Day       0.6761043  1 4.109314e-01
#Time     35.8647640  3 7.997949e-08
#Day:Time 14.3020921  3 2.521503e-03

## ANOVA-type statistic
ex.f2$ANOVA.test

#          Statistic       df      p-value
#Day       0.6761043 1.000000 4.109314e-01
#Time     14.2671950 2.858344 5.860479e-09
#Day:Time  5.2242782 2.184249 4.150298e-03