The main objective of this study is to analyze the impact of macroeconomic uncertainty on economic growth and investment in Iran during 1980 to 2011 (1359 to 1390 corresponding to Iranian calendar). Hence, macroeconomic uncertainty vectors for both macro indicators, including the budget deficit and the volume of money are estimated using the generalized AUTOREGRESSIVE CONDITIONAL HETEROSKEDASTICITY (G(ARCH)), and the impact of each macroeconomic uncertainty vectors on investment and economic growth is studied. The results show that the macroeconomic uncertainty indicators have statistically significant negative impact on investment and economic growth in Iran during the mentioned period. So that increasing 1 percentage in the budget deficit uncertainty causes to decrease 0.23 percent and 0.31 percent in investment and in economic growth, respectively, and also increasing 1 percentage in the money uncertainty leads to reduce 0.25 percent in investment and 0.17 percent in economic growth. In addition, the budget deficit uncertainty has had more effect on reducing in economic growth and investment than the money uncertainty.

Inflation has always been an economic problem and different solutions have been proposed to control it. Although it is said that "higher output lowers inflation rate" but it is true when other factors are constant. This study se(ARCH)es the answer to the following question: "what is the effect of inflation rate and output in a case that inflation rate and output growth has a volatility trend?" To this aim we use seasonal data on Iran’s gross domestic product and consumer price index from spring1975 to summer 2008 and an exponential generalised AUTOREGRESSIVE CONDITIONAL HETEROSKEDASTICITY (EG(ARCH)) model to show volatility the variables.The results of this study show that there is an AUTOREGRESSIVE CONDITIONAL HETEROSKEDASTICITY ((ARCH)) process in the output growth and inflation rate. We also find that the inflation rate and output volatility increase Inflation rate and the output volatility higher output growth. The hypothesis that the inflation rate volatility lowers output growth can not be accepted.

In this paper, we investigate variations of gold coin price and also probe to model the fluctuations and CONDITIONAL variance of coin market returns. The data consist of daily market prices of gold coin over the 1380 – 1386 period. Since volatility clustering is viewed in time series of returns, we employ (ARCH) (AUTOREGRESSIVE CONDITIONAL HETEROSKEDASTICITY) methodology in order to model the variance of returns. The results suggest that EG(ARCH) is the best choice among other models of the (ARCH) family. The fluctuations are influenced by oil price and exchange rate.Exchange rate has the greater effect than oil price on CONDITIONAL variance. Leverage effects were observed in gold coin market. It means that good news have greater influence rather than bad news with equivalent magnitude.