The Pacific Decadal Oscillation (PDO) index defines the leading mode of monthly sea surface temperature anomalies in the North Pacific Ocean. Time series analysis in both the frequency and time domains is applied to 107 years of monthly PDO index values. Simulations of a model fitted to the data are examined for the occurrence of particular event seen in the raw data; a probability for this event is calculated. The simulations are further used to tabulate histograms for mean length (in years) of a positive phase, and the absolute difference between the longest positive and negative phase (in years). The results show that the probability of occurrence of the event in the raw data is relatively low (9.9%). The raw data's mean positive phase length is close to the simulation mean and median, while the absolute difference in maximum positive/negative phase lengths corresponds to a p-value of 14.9%.