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Change point detection is one of the most challenging statistical problems because the number and position of these points are unknown. In this article, we will first introduce the concept of change point and then obtain the parameter estimation of the first-order autoregressive model AR(1); in order to investigate the precision of estimated parameters, we have done a simulation study. The precision and consistency of parameters were evaluated using MSE. The simulation study shows that parameter estimation is consistent. In the sense that as the sample size increases, the MSE of different parameters converges to zero. Next, the AR(1) model with the change point was fitted to Iran's annual inflation rate data (from 1944 to 2022), and the inflation rate in 2023  and 2024 was predicted using it.

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Integer-valued time series models play an essential role in the analysis of dependent count data. One of the main challenges in these models is to detect structural changes over time. These changes may be caused by sudden interventions such as policy changes, pandemics, or system failures. In this paper, the empirical likelihood method is used to detect structural changes in a class of INAR(1) processes. This method is a tool for early warning of structural changes in these processes. Using simulation, the empirical sizes and powers of the test are calculated for different sample sizes, and the test's performance is investigated. Finally, the practical efficiency of the test is investigated by identifying the change point in two real datasets: the number of robberies and the number of COVID-19 deaths.