The present search aims to develop a test for selective attention, cognitive load and thinking mistakes and measuring these concepts among Baghdad university students. To make a comparison between the selective attention, cognitive load, and the mistakes of thinking among students in term of gender. To identify the relationship among the selective attention, cognitive load and the mistakes of thinking of university students. To achieve these purposes, the searcher has developed a test for selective attention, cognitive load, and the mistakes of thinking. Then, these tools were applied to a sample of (200) university students were selected from (21) college. The researcher used t-test of one sample, t-test of two independent samples, multiple correlation coefficient, and partial correlation coefficient. The findings revealed that students have a good level of selective attention, cognitive load, and the mistakes of thinking, Males differ from females in selective attention, students have a high level of selective attention compared to cognitive load and the mistakes of thinking. And finally, there is a strong relationship between selective attention, cognitive load, and the mistakes of thinking. To conclude, the searcher suggested some studies: the relationship between selective attention and rational thinking. The relationship between cognitive load and disorder thinking. The relationship between the mistakes of thinking and democratic thinking.
In order to serve the field of knowledge in the field of design and analysis of experiments by adopting formulas and methods that are easy and simple in arithmetic work, especially in experiments that require many calculations for squares, including tests of type
