# Can I use Mann-Whitney-U test for this?

#### lyralice

##### New Member
Hi guys!
For my bachelor thesis I am desperately trying to figure out this statistical problem ...

I am comparing two curves: The course of the concentration of protein A versus the course of the concentration of protein B. I measured the concentration at 3 different times (0h, 12h, 24h) and n = 12 measurements per time per protein

Protein A:
0h: 2, 3, 2, 4, 3, 3, 4, 2, 2, 3, 4, 2
12 h: 5, 7, 4, 5, 5, 6, 4, 5, 7, 5, 5 , 5
24 h: 8, 9, 8, 9, 10, 7, 8, 8, 9, 8, 7, 8

Protein B:
0 h: 5, 6, 4, 5, 6, 5, 6, 4, 6, 6, 6, 7
12 h: 8, 9, 9, 9, 8, 9, 8, 9, 8, 9, 9, 9
24 h: 10, 13, 12, 12, 13, 12, 13, 12, 14, 12, 10, 11

So Protein B has a higher concentration and the concentration raises more over time in comparison to Protein A.
I want to know if the difference is significant.

Can I use the Mann Whitney U test for this?
I have managed to compare the two medians of Protein A (0h) vs Protein B (0h) - so each median at a given time - with the Mann Whitney U Test, but I don't manage to compare the two curves...

If someone could help me out I'd be forever grateful!

Lea

#### Karabiner

##### TS Contributor
Can I use the Mann Whitney U test for this?
No. Definetly no.
If someone could help me out I'd be forever grateful!
Ok, what did your instructor propose?

With kind regards

Karabiner

#### lyralice

##### New Member
My instructor proposed the Mann Whitney U test ... then I did some research and started to doubt it.
Is there any other specific test that you can recommend?

#### Karabiner

##### TS Contributor
Are these 2*12 samples, each sample was measured three times, and you can relate each
measurement to the individual sample where it came from? In that case, you could
do a mixed analsis of variance with n=24, a repeated-measurement (within-subjects)
factor "time" and a grouping (between-subjects) factor "protein type". The interaction
between the factors tells you whether the concentrations raise differently over time.

With kind regards

Karabiner