were also recorded. Embryo recovery outcomes
(-1 or þ1) were summed, starting from the lowest to
the highest sperm quality value to give a CUSUM for each
sperm quality measure. The results were described in
graphic form with sperm quality values plotted in
ascending order on the x-axis and cumulative embryo recovery
values on the y-axis. The intent of this approach was
to identify changes in fertility as the sequential variable
(i.e., measure of sperm quality) increased. An example of
this approach is represented in Supplemental Material. The
point at which the slope of the graph changed was
considered a threshold value for that measure. For
example, a slope of zero (horizontal line) would represent
an ERR of 50% per cycle, with no change occurring because
of a sequential increase in the measure plotted. A positive
slope would represent an increase in ERR as the measure
increased, whereas a negative slope would indicate a
decrease in the ERR as the measure increased.