Solved – interpretation from loess graph

loessrstatistical significance

I have measured events X and Y in two strains (A and B) of same species. After calculating the values of these X and Y, I compared them with wild type values (X and Y) to calculate fold change. I have plotted these fold changes of X and Y in A and B, and curve was fitted with LOESS. enter image description here

Now for event X (top plot) LOESS approximates to straight line, but for event Y (bottom plot), the smaller values (Chromosome size < 600 kb) seem to be elevated.

My question is by just showing this plot can I claim that smaller chromosomes get more event-Y than larger chromosomes (chromosome size > 600 kb) or do I need to do statistical tests to say this ?? If so what tests do you suggest ?

Sorry I am poor when it comes to advanced statistics. Hope I have clearly stated my problem.

Best Answer

Welcome to the site.

You can say that smaller chromosomes get more Y-event than larger ones based on this graph; if you want to say that they get significantly more then you need some sort of statistical test.

If you are using R then the rms package offers tests of splines and loess fits.

If you are using SAS there is PROC LOESS.

Several interesting things seem to be going on in your two graphs; you didn't ask about this, but did you note that for X, the A curve is higher and for Y the B curve is? This might be interesting.

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