In this letter, we propose a packet loss probability (PLP) assessment method that uses active measurements. Considering the statistical nature of measurement data in a network, we adopt the confidence interval to assess whether the performance of a network complies with a target PLP or not. Using both analysis and simulations, we show that the proposed method can guarantee that the probabilities of erroneous assessments are not more than a given significance level. In addition, we provide a systematic method to determine the number of probing packets needed for statistical assurance by presenting a clear relation between the assessment accuracy and the measurement overhead.