Scientists use the chi square analysis in order to determine whether differences between expected and observed data are attributable to chance or an extraneous factor unaccounted for in the experiment. The null hypothesis for a chi square analysis is always the same: Any difference between the observed and expected data is due to chance. The goal of this experiment is to confirm or refute this null hypothesis.
The hypothesis is inconsistent with the observed data and the chi square analysis has determined that the null hypothesis was incorrect, meaning that the difference between observed and expected data in this experiment is not merely due to chance. The rejection of the null hypothesis means that extraneous factors are influencing the data. The most obvious explanation in this case would be that the Mars Company sorters did not distribute different-colored M&Ms in each package according to the information on their website.