Table 1. Summary of descriptive statistics of the 6-week-long fibroblast recordings (n = 80 cells from 2 cultures).

	Mean±SD
Period (MESA)	25.02±0.87 h
Period (mean peak-to-peak time)	24.93±0.87 h
Period CV (peak-to-peak times)	0.074±0.023 (Median 0.073)
Amplitude of cells (mean peak-to-trough distance)	3.56±1.69 photons/min
Amplitude CV (peak-to-trough distances)	0.39±0.12 (Median 0.37)
Brightness	2.38±0.94 photons/min
Image area of cells	9250±2120 µm2

After eliminating several days at either end of the data series to avoid edge effects and initial transients, 34 cycles were used for calculating cycle length and amplitude statistics of each cell. The period of each cell's time series was calculated using maximum entropy spectral analysis (MESA) and also as mean peak-to-peak time. Coefficient of variation (CV), a dimensionless measure of variability, equals the standard deviation divided by the mean. Brightness (photons/min) equals mean intensity over 34 days of recording.