The role of feeling regret in the investor's mass behavior in psychological and financial decision-making with an emphasis on buying and selling positions

The evidence shows that investors in the Tehran Stock Exchange, in addition to quantitative methods, used judgments based on subjective perceptions, non-scientific information, rumors and blindly following a few participants in the capital market to determine the stock value. It is also known as collective, herd and mass behavior. Therefore, the purpose of the current research is the role of regret in the decision-making of the investor's collective behavior in the buying and selling situation. This research is applied in terms of purpose and descriptive-survey in terms of type. The statistical population of the research includes all the shareholders in the stock exchange, which was calculated as 384 people according to the unlimited population to obtain the statistical sample size using Cochran's formula. And the test made by the researcher to determine the feeling of regret of the investor's mass behavior in the buying and selling situation was carried out on them, the results were analyzed using SPSS and Smart PLS statistical software. The results showed that the reliability and convergent and divergent validity of the appropriate model and the fit of the structural equations and overall fit were strong, and the feeling of regret had a positive and significant effect on the financial and psychological decision-making of mass investors.