Which test to use

#1
Hi!
I am making a small scientific research and would really appreciate some home with statistics.
Excel file is in the attachment.
I am studying the expression of two similar markers in carcinomas depending on grade (column „grade”). There are 6 different grades GG0-GG5. The markers are FM and SM, the expression values are in %. The correlation coefficient between SM and FM is 0,8, the expression is pretty similar, but FM theoretically should be slightly better. What statistic should I use to prove that one marker is better than another meaning correlation between marker expression and GG is better? I know that the word „better” is not very scientific :) The solution should be quite simple, but I failed to find it by myself. I have stata and R
Apologies for my English.
Thank You in advanced.
 

Attachments

obh

Active Member
#2
Do you want to see the best combination of FM and SM as predictors to grade, like Grade = 5.855577 - 0.121474 FM - 0.0235641 SM?
FM pval=0.00000
SM pval=0.00252555
like linear regression or better ordinal logistic regression?

Do you want to prove that FM is better than SM as a predictor for the grade? you may run two models and see which one gets better result
 
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obh

Active Member
#5
I can see both markers are significance with linear regression but the FM had lower p-value as you expected.
I assume you will have a similar result with ordinal regression, but you should try.
linear regression is okay but ordinal is better for your case.
 

obh

Active Member
#7
Yes, the link is correct, shouldn't be too complex :)
The values were for linear regression with 2 predictors, but you get similar results (say better for FM) with one linear regression model per predictor.
So probably similar results also for ordinal, but you should try
 

Karabiner

TS Contributor
#9
It seems like you want to statisticaly compare "correlated" correlation coefficients.
You could use correlated correlations coefficients as a search string in a web search.
An online calculator (with references) for such analyses you can find here.

With kind regards

Karabiner
 
#10
It seems like you want to statisticaly compare "correlated" correlation coefficients.
You could use correlated correlations coefficients as a search string in a web search.
An online calculator (with references) for such analyses you can find here.

With kind regards

Karabiner
Hi!
Although the example in Your link seems quite simple, I had some issues.
As I understand, the step by step solution would be:
1) correlation between GG and FM
2) correlation between GG and SM
3) use the calculator.
As I have only basic knowledge in statistics, I have some questions :)
GG is a discrete variable, with values 0,1,2,3,4,5. How do I correlate it with %?
Where do I get r3 for the calculator?
My apologies for these primitive questions.
 

obh

Active Member
#12
I will try it!
Final questions:
What software would You advise?
I do not understand what are these values?
Hi Kate,

I just transform the Grade to numbers (GG0=>0, GG1=>1 etc ....) and ran multiple regression with an online calculator.
I suggested running ordinal regression on each mark separately and see which one will give a better result, but in statistics, there is not only "better result" you should also prove it is significant and not just a random result, and that what @Karabiner suggested. So please do as @Karabiner suggested.

Cheers