فصلنامه تحقیقات حسابداری و حسابرسی
پیاپی 55 (پاییز 1401)

This research aims to provide a systematic review of the effect of independence of internal audit unit on the effectiveness or performance of internal audit by meta-analysis method. For this purpose, studies internal and external performed over the period of 1390-1400 were reviewed and discussed. The present meta-analysis has provided a statistical combination of the findings of the previous studies on the effect of independence of internal audit unit on internal audit performance. The results showed that most studies had a significant effect size. Regarding the measurement error of the homogeneity test (less than 0.05), the studied research works are homogenous. It suggests the approval of constant effects model. On the other hand, constant effect model was evaluated at a medium level based on Rosenthal Table. Meanwhile, the measurement error of the constant effect model is less than 0.05 and it approves the research hypothesis. So, internal audit independence is effective in internal audit performance.

The profitability of the companies and factors affecting it is an issue of interest in financial and accounting research. The purpose of this study is to investigate the effect of agency costs and management ability on the profitability of companies, and the way agency costs affect profitability by emphasizing the role of management ability.

Data of 100 companies accepted in Tehran Stock Exchange was collected during the years 2012 to 2018.  In order to measure profitability and agency costs, the ratio of return on assets and inverse of assets utilization ratio were used respectively. The management ability was measured using the two-stage method of Demerjian et al (2012). Data analysis was performed using Data Envelopment Analysis and EViews10 software.

The results show that the index of agency costs has a negative and significant effect on the profitability index. According to the GMM Panel (dynamic model), management ability also has a positive and significant effect on future profitability. On the other hand, the managerial ability moderates the impact of agency costs on profitability by reducing its negative impact on the profitability index.

The results indicate that managers with high abilities can better align their interests with those of shareholders and the agency conflicts such as moral hazard, earnings management, time horizon difference and the tendency to maintain profit inside the company, occur in companies with such managers less.

Since tax constitutes a major part of the government's income and is the most common and most important method of providing government spending to ensure social welfare and economic growth, therefore regardless of taxes and important factors in avoiding paying taxes, economic growth and increasing public welfare in the long term It is not possible. Therefore, the main purpose of the research is to examine the relationship between the effective tax rate and the risk of companies listed in the Tehran Stock Exchange, emphasizing the components of tax culture. The data of this research includes the financial information of listed companies from the beginning of 2007 to the end of 2016. In this research, the panel data model was used to check the hypotheses. The results showed that there is a significant and direct relationship between the lower effective tax rate and sub-indices of tax culture (tax laws, crimes and forgiveness, awareness, social justice), with future tax rate fluctuations and future stock price fluctuations. Therefore, it is necessary to use the funds from tax avoidance activities in the field of investment to increase the expected future cash flow and as a result reduce the cost of capital.

The success of any asset pricing model should depend on the proportionality of the real options in the value of the companies whose returns are tested in the model test. The purpose of this study is to investigate the Investment Option Model Indicators and its impact on stock returns. The statistical population of this study consisted of 146 companies in the period 1390-1397. This research is applied in terms of and in terms of nature and content is correlational and the research hypotheses are estimated using multivariate regression approach and panel data method. The results of the hypotheses test showed that investment options based on Grullon's four-factor model affect stock In addition, the results showed that there is a significant difference between the explanatory power of Fama and French's five-factor asset pricing model and the investment options model based on Grullon's four-factor model in explaining stock returns. And the explanatory power of the Grullon's four-factor model in explaining stock returns is more than the Fama and French five-factor model.

The purpose of this research is investigating the effect of unexpected cash changes on surplus returns in uncertainty conditions in companies which listed in Tehran Stock Exchange during 2010-2016. In this research, the unexpected changes in the cash were considered as independent variable and the surplus returns were considered as dependent variable. The current research is a descriptive and applied research. It is also considered as a correlation in the research category.Based on the systematic elimination method, 147 companies were selected as the statistical sample. In order to analyze the data, variance heterogeneity pre-test, F Limer test, Hausman test and multivariate regression test were used to confirm and reject the research hypotheses (EVIEWS software).  The results showed that there is a significant and positive relationship between unexpected cash changes and surplus returns; in addition, the economic and special uncertainty conditions affect negatively the relationship between unexpected cash changes and surplus returns.