How does daily amount of sleep vary within and between healthy adults? I'm interested in research that has employed the following or similar research design:


Measure the daily amount of sleep 
every day for an for an extended period (e.g., more than a month)
in a relatively large sample (e.g., $n &gt; 100$) of "normal" healthy adults


This would give rise to sleep measurements on multiple days and for multiple individuals. Thus, we could define $y_{ij}$ as the amount of sleep of person $i$ on day $j$. Descriptive statistics could be calculated on the set of daily sleep measurements of person $i$ such as the mean and standard deviation. These within-person descriptive statistics could also be summarised at the group-level.

Questions

In general, what are the main descriptive statistics of such data?

More specifically, I'd be interested in knowing:


What is the mean of the within-person mean of daily amount of sleep?
What is the standard deviation of the within-person mean of daily amount of sleep?
What is the mean of the within-person standard deviation of daily amount of sleep?
What is the standard deviation of the within-persons standard deviation of daily amount of sleep?


Presumably such results are contingent on how sleep is defined and measured, as well as many other factors such as the nature of the target population. Thus, any comments about these factors would also be welcome.
Just a starting point.
Jean-Louis et al (2000) provide one sample of population adult sample using objective sleep measures. To quote the abstract


  Using Actillumes, we investigated whether self-reported sleep
  durations were indicative of a population decline in sleep duration.
  We also explored illumination and activity patterns. Methods: San
  Diego adults (n = 273, age range: 40–64) were recruited through random
  telephone calls and were monitored at home while engaging in usual
  daily routines. Results: Volunteers slept an average of 6.22 hours and
  received an average of 554 lux (environmental illumination). The
  timing of sleep, illumination, and activity occurred at 2:44, 12:57,
  and 13:43, respectively.


References


Jean-Louis, G., Kripke, D.F., Ancoli-Israel, S., Klauber, M.R. &amp; Sepulveda, R.S. (2000). Sleep duration, illumination, and activity patterns in a population sample: effects of gender and ethnicity. Biological psychiatry, 47, 921-927.