Index selection block

While costing index access, dbcc traceon(302) prints a set of statistics for each useful index. This index block shows statistics for an index on au_lname in the authors table:

Estimating selectivity of index ’au_names_ix’, indid 2
   scan selectivity 0.000936, filter selectivity 0.000936 
   5 rows, 3 pages, index height 2,
   Data Row Cluster Ratio 0.990535,
   Index Page Cluster Ratio 0.538462,
   Data Page Cluster Ratio 0.933579