[R] sleep data

[Tom Backer Johnsen]

When reading the documentation for the "sleep" data set in R, the 
impression is clear, this is an "independent groups" kind of design 
(two groups of 10 subjects each).  However, when browsing the original 
article (referred to in the help file), my impression is quite clear, 
this is really a "repeated measures" kind of data (one group of 10 
subjects, two observations).  What is correct?

Tom