warm greetings to all Drs , Mrs.
did any one have and idea what supposed to do in statistical analysis for research , I have a sample composed from 135 patients , each patient I got 8 categorical variables and 8 quantitively variables , 135 patient grouped to 3 groups class I , Class II and Class III by one parameter called ANB and 3 groups Short , Average and Long face by another parameters called FMA , also two groups be gender Male and Female , I did the normality test for 8 quantitative variables and I got some of variables statistically significant and others not , now my question is how can we conduct normality test for categorical variables especially I define the variable as string , did I need to change it to numeric ?
second question did I need to conduct the same test for statistically significant and statistically non significant variables in normality test ? I mean parametric and non parametric test ? which one I should choose according to p value
if I need to conduct non parametric test how can I do it if my data composed from three groups .
I'm so sorry for my English language , and i hope anyone have any helpful source just post it here .
thank you all.
The normality test is used to determine the data residuals are normally distributed. So, the residual data tested is not a variable
Dear Ahmad,
1) You can not do any analysis with string type of data. you should attach them a number (simply add a new variable, and then give them numbers).
But, for testing normality of data, some consider categorical data as not normally distributed, so do not conduct any normality test.
2) Some papers did normality tests, and some did not. but if you want to do normality test, so just simply choose parametric test for normally distributed variables and vice versa.
3) Based on your research aims, it can change. For example, imagine you have three groups, and you want to looking for significant difference between the mean values. in this regard, you should choose one way ANOVA (parametric test) or Kruskal-wallis (non parametric). because you have three groups.
If you can be little bit clearer about your research framework, I'll help you efficiently.
As Dr khoushe vatan said, categorical data are not normally distributed. If you want to check the normality of a scale (like some of them) you can slush the plots and tests like SK.
Mohammad Sofyan Babak Jamshidi Mohammad Ali Koushesh Vatan thank you so much for paying attention ,DR. Mohammad Ali Koushesh Vatan
i already did it changed the string to numeric variable and defined the values , now the point is related to normality test some p value less than 0.05 which need to conduct non parametric test and some p values more than 0.05 which need to perform parametric tests this according to which i know and actually I'm not professional in it , so if i misunderstood it please correct me , and if you have time just let me know , ill be so glade to discuss this matter with you dr mohammad ali .
Your welcome,dear Ahmed.
Yes, that is right.
Feel comfortable to ask any question. İ will try to answer, if i can.
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