The scatter in laminar flame front speed caused by both an error in the composition of the combustible mixture and initial disturbances is reported. It's shown how the configuration of the initially planar front in laminar flame initial disturbances in a gas mixture of the same composition affects the scatter of speeds of expanding spherical flames. The experimental results previously obtained by the authors, demonstrating the scatter in the speed of the laminar flame front in an initially quiescent gas mixture of constant composition under the same conditions, are explained by integrating the Sivashinsky equation with various initial disturbances. The influence of combustible mixture composition errors on the parameters determining the speed of the flame front is analyzed. These parameters were recalculated for a possible scatter in the mixture composition, obtained based on data on the accuracy of the equipment used in previously published experiments.