To take into account the temperature fluctuation in the Planck distribution, we calculate convolution integral with several probability distributions. Using these formula as well the Planck distribution and a formula in the non-extensive statistics, we analyze the data measured by the Cosmic Background Explorer (COBE). Our analysis reveals that the derivation from the Planck distribution is estimated as |q-1| = 4.4\times 10^{-5}, where q means the magnitude of the non-extensivity or the temperature fluctuation, provided that the dimensionless chemical potential proposed by Zeldovich and Sunyaev exists. Comparisons of new formulas and the Planck distribution including the Sunyaev-Zeldovich (S-Z) effect are made.
Comment: 8 pages, 2 figures, REVTEX4