smoothing voltage to sensor?

hey everyone, i am using a sharp infrared sensor, https://www.sparkfun.com/products/242 with 5v Uno,
and I'm getting some inaccurate values, (+/- 3-5%) and i want to add a capacitor to prevent voltage spikes. however, I've been unable to find any wiring guide, and i don't know how many Farads the cap should be. thanks.

add a capacitor to prevent voltage spikes

For transient protection

o/p---100R---.1uF----100R----Analog i/p
|
|
GND

But this won't do anything for inaccurate values.