Cost data intended for Monte Carlo analysis can be in either 2-point or 3-point format.
2-Point (Base+Contingency) Format
Cost is entered in terms of a base amount plus a contingency. For example, $1000 + 10% contingency implies that you expect to spend $1000, and, depending on circumstances, may spend up to an extra 10%.
3-Point (Mid/High/Low) Format
Cost is entered in terms of a base, or mid-range, amount with variances. For example, a cost entered as $1000 +/-10% means that you think the cost will be somewhere around $1000, but are not sure of the exact amount. In this case the cost has been expressed as a range which is equivalent to 'somewhere between $900 and $1100'.