In a genetics experiment, investigators examined 300 chromosomes of a particular type and counted the number of sister-chromatid exchanges on each one (?On the Nature of Sister-Chromatid Exchanges in 5-Bromodeoxyuridine-Substituted Chromosomes,? Genetics, 1979: 1251-1264). A Poisson model was hypothesized for the distribution of the number of exchanges. Test the fit of such a model to the accompanying data by first estimating A and then combining the frequencies for x = 8 and x = 9.

x: 0 1 2 3 4 5 6 7 8 9 Frequency: 6 24 42 59 62 44 41 14 6 2