A method for estimating a probability of failure of a least-squares ambiguity decorrelation adjustment (LAMBDA) method is provided. The LAMBDA method is used for estimation of double difference carrier phase integer ambiguity. A plurality of condition sets are selected. Each condition set comprises a probability of failure (Pboot-fail) for a boot-strap method of estimation of the double difference carrier phase integer ambiguity, a number of space vehicles (Nsv), and a ratio test tolerance for the LAMBDA method. A plurality of Monte Carlo simulations are run on the plurality of condition sets to obtain a plurality of result sets. Each result set comprises a probability of lambda fail (Pλ-fail) and a probability of lambda reject (Pλ-reject) for one condition set of the plurality of condition sets. A lookup table is created with the plurality of result sets. A value of Pλ-fail for given values of Pλ-reject, Pboot-fail, and Nsv is estimated through employment of the lookup table.