You know that I've blogged before about the danger of PMs taking a single-point estimate. I want to draw your attention to a nice talk given by Chimamanda Adichie (shown on the left) called, "The Danger of the Single Story".
I'd like to acknowledge Pervez Mohammed of VISIONS non-profit group for making me aware of this video.
It takes the idea of a single-point estimate to a whole new level.
Listen to her. The video is about 20 minutes and is located HERE.
Then think. Or maybe reflect is a better word here. Think about using this as you identify risks, as you build your teams, as you take inputs from contributors. Don't rely on one source. As a PM you need to be unbiased and open to wider sources of information and willing to listen to alternate versions.
This talk may help you with that.