assignment 1

# assignment 1 - Alicia Deal CJ 771 Assignment#1 Time Series...

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Alicia Deal CJ 771 03-27-07 Assignment #1: Time Series Analysis 1.) Construct an ARIMA model for homicide for the state you have been assigned. Include a) examination of the autocorrelation function (ACF) and partial autocorrelation function (PACF) both before and after estimation, b)the coefficients and their statistical significance, and if possible c) results from the Dickey-Fuller test at pre-estimation and goodness of fit tests (such as AIC, BIC, SBC) post-estimation. Interpret the results. The autocorrelations indicate that the means are non-stationary (all Box-Ljung coefficient values are significant at p<.001), while the ACF & PACF graphs show several outliers. Hence, differencing was conducted in order to make the model stationary. The differencing represents the changes in homicide rates over the 40 year period; in this case one trend appears. Once differencing had been conducted, the graphs are now within the confidence levels, and all coefficients, with the exception of lag 2 (p<.05), are no longer significant. The shape of graphs indicates that a moving average process may need to be added to the model (0, 1, 1). The parameter estimate for this model is (.124) and has a t value of (.073) with a significance of (.289). However, the AIC value (129.265) and BIC value (132.966) indicate that this model is not an adequate model for homicide rate. Therefore, the appropriate model is (0, 1, 0). The AIC value is 128.373 and the BIC is 130.223 suggesting a good fit of the model.

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assignment 1 - Alicia Deal CJ 771 Assignment#1 Time Series...

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