While investors of all stripes have had their confidence in the markets badly shaken, those sitting on a rollover from an individual retirement account, an inheritance or other windfall are in a particularly tough spot.

Should they invest the money all at once (so-called lump-sum investing) or dribble it into the markets in equal increments over a period of months or years (dollar-cost averaging)?

The answer depends, in part, on whether they are more concerned with maximizing their long-term returns or minimizing their short-term risk of losses