Summary1. Sample mean intensity (XN) in successive N alpha waves is similar to the product of sample number of alpha component (ηN/2) and sample mean intensity of an alpha component (2rϕ/N) in the same N alpha waves, i. e.(7.6) X̄n=ηNσ2/N2. In many human EEG data under a relaxed state, the points (ηNσ2/N) form a rectangular hyperbola and the points (logηN, logσ2/N) form a straight line with a gradient of fourty five degrees, because of the very small fluctuation of sample mean intensity Xn.3. Above results are obtained not only in alpha rhythms, but also in theta rhythms.4. Herewith an important possibility arises in sofar that in the characterisica of the above straight line or band some biological meaning, apart from the resultant from sample mean amplitude or sample mean intensity of brain waves is strongly s