It can be seen through the interaction diagram between factors. Other factors (c, d ...) remain unchanged. If there is no interaction between factor A and factor B, the interaction curve (dotted line) between different levels of factor A and factor B should tend to be parallel; If there is interaction between factor A and factor B, the interaction curve (dotted line) between different levels of factor A and factor B should be obviously crossed or seriously unbalanced.

Of course, it can also be determined by inspection. H0: The interaction between factor A and factor B is significant. Calculate the variance of interaction, calculate the variance of error, and then divide the two to construct an F test, and judge whether there is interaction through the results of the F test. The principle of this F test is the same as judging whether the factor effect is significant.

Reference book: experimental design-Yan; Experimental design and data processing-Zhang Chengjun.

I hope I can help you.