Thursday’s big drop moved the SPX strongly down through its 50-day moving average.  And it did so with both breadth and volume providing exclamation marks.  Such breaks of highly public support lines like the 50-day moving average can be notable (and it certainly drew attention on Thursday).  Some traders may view it as a change in trend.  And while it may be when looking out over a period of days, weeks, or months, the immediate 1-day reaction to such moving average breaks has typically been to bounce.  This can be seen in the study below.

The 15 for 16 record is very impressive, and suggests a good chance of the market closing higher today.  The average instance gained about 0.6% on the day.