Two mathematicians have proved that a straightforward question—how hard is it to untie a knot?—has a complicated answer.

In a variety of problems involving models from genetics, latent-class analysis, and missing data, I apply a log-linear model to an indirectly observed frequency table. Current algorithms for ...

*The buy-the-dip impulse still seems to be missing. *Market participants have become more discerning in their review of earnings results. *The Russell 3000 Growth Index is down 2.7% for the week, ...