sleepstudy: Reaction times in a sleep deprivation study

Description Format Details References Examples

Description

The average reaction time per day (in milliseconds) for subjects in a sleep deprivation study.

Days 0-1 were adaptation and training (T1/T2), day 2 was baseline (B); sleep deprivation started after day 2.

Format

A data frame with 180 observations on the following 3 variables.

Reaction

Average reaction time (ms)

Days

Number of days of sleep deprivation

Subject

Subject number on which the observation was made.

Details

These data are from the study described in Belenky et al. (2003), for the most sleep-deprived group (3 hours time-in-bed) and for the first 10 days of the study, up to the recovery period. The original study analyzed speed (1/(reaction time)) and treated day as a categorical rather than a continuous predictor.

References

Gregory Belenky, Nancy J. Wesensten, David R. Thorne, Maria L. Thomas, Helen C. Sing, Daniel P. Redmond, Michael B. Russo and Thomas J. Balkin (2003) Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study. Journal of Sleep Research 12, 1–12.

Examples

1
2
3
4
5
6
7
8
9
str(sleepstudy)
require(lattice)
xyplot(Reaction ~ Days | Subject, sleepstudy, type = c("g","p","r"),
       index = function(x,y) coef(lm(y ~ x))[1],
       xlab = "Days of sleep deprivation",
       ylab = "Average reaction time (ms)", aspect = "xy")
(fm1 <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy, subset=Days>=2))
## independent model
(fm2 <- lmer(Reaction ~ Days + (1|Subject) + (0+Days|Subject), sleepstudy, subset=Days>=2))

Example output

Loading required package: Matrix
'data.frame':	180 obs. of  3 variables:
 $ Reaction: num  250 259 251 321 357 ...
 $ Days    : num  0 1 2 3 4 5 6 7 8 9 ...
 $ Subject : Factor w/ 18 levels "308","309","310",..: 1 1 1 1 1 1 1 1 1 1 ...
Loading required package: lattice
Linear mixed model fit by REML ['lmerMod']
Formula: Reaction ~ Days + (Days | Subject)
   Data: sleepstudy
 Subset: Days >= 2
REML criterion at convergence: 1404.094
Random effects:
 Groups   Name        Std.Dev. Corr 
 Subject  (Intercept) 31.507        
          Days         6.766   -0.25
 Residual             25.526        
Number of obs: 144, groups:  Subject, 18
Fixed Effects:
(Intercept)         Days  
     245.10        11.44  
Linear mixed model fit by REML ['lmerMod']
Formula: Reaction ~ Days + (1 | Subject) + (0 + Days | Subject)
   Data: sleepstudy
 Subset: Days >= 2
REML criterion at convergence: 1404.626
Random effects:
 Groups    Name        Std.Dev.
 Subject   (Intercept) 28.843  
 Subject.1 Days         6.285  
 Residual              25.747  
Number of obs: 144, groups:  Subject, 18
Fixed Effects:
(Intercept)         Days  
     245.10        11.44  

lme4 documentation built on June 22, 2021, 9:07 a.m.