If you slide your observation period forward or back, those bad returns often disappear fast.

FORBES: Lost Decade, Found!

During the observation period, 1, 156 patients (28.4 percent) died, with 879 (76.0 percent) of these deaths related to cardiovascular disease.

FORBES: Longer Warfarin Therapy After Bioprosthetic Aortic Valve Replacement May Be Beneficial

But right after his observation period was up, before Weaver could retrieve the model, another car moved to the right to hit the animal as he stood less than 20 feet away.

MSN: College student's turtle project takes dark twist

Over the three-year observation period, the African-American students who took part in the study had higher grade-point averages relative to multiple control groups, and the minority achievement gap overall was reduced by a dramatic 50%.

CNN: The importance of belonging

In this valuable and well written account of that period, Josephine Woll spotlights an observation by a Russian writer, Vitaly Troyanovsky.

ECONOMIST: Soviet cinema

We can see things -- we pass over the same portion of the Earth every day, so it's a regular observation that we can make over a long period of time, as well.

WHITEHOUSE: President Obama's call to the International Space Station

That hypothesis is supported by the observation that soot levels fell during the 1970s, a period when many European countries enacted clean-air regulations.

ECONOMIST: Pollution in the Himalayas