Suppose we have 4 measurement of vision angles peripheral and clear in horizontal and vertical ,and the drivers tests cases as 1 with head cover 2 with spectacle 3 with head cover and spectacle 4 without any thing , how can we enter the effect of tradition wearing the 4 cases on reaction time and the rate of accidents knowing that head cover and spectacle is having the biggest effect on vision abilities , can we use the four cases as one variable with factors assumed 1,2,3,4 with ordinal measurment or nominal or scale .or we must seperate the cases into 2 variable (spectacle yes, cover, yes or no),and what is the measurment of the two cases scale nominal ordinal) ,how can we assume the value of each case depending on what. i want answer to my question and if you found the question too long tell me to post it in seperated question as you tell me about it(the answer using spss program).