Do extinctions occur randomly through the long fossil's record of Earth's history?, or are there periods in which extinction rates are unusually high ("mass extinctions") compared with background rates? Whitlock and Schluter (2009) give data on the number of extinctions of marine invertebrate families in 76 blocks of time of similar duration. 0 extinctions happened in none of the blocks 1 extinction happened in 13 blocks 2 extinctions happened in 15 blocks 3 extinctions happened in 16 blocks 4 extinctions happened in 7 blocks 5 extinctions happened in 10 blocks 6 extinctions happened in 4 blocks 7 extinctions happened in 2 blocks 8 extinctions happened in 1 block 9 extinctions happened in 2 blocks IV 10 extinctions happened in 6 blocks Estimate the expected number of extinctions per block given the data above and compare the proportion of blocks predicted by the model for each of the above extinction numbers with the observed ones. Is there much difference between the two? After providing those in a nice table, do the chisquare test that is being done in the supplementary document on births, by adding the counts to the table, both the counts observed and the predicted ones