# what does the slope and efficiency tell us - (Feb/07/2007 )

I am running standard curves for my housekeeping genes and the slope and correlation coefficient look good (3.5, and >.990, respectively). I understand that the slope indicates that the primers are amplifying lin a linear fashion. What is the R2 actually an indication of ?? Is it an indication of how precise the dilutions are? Thanks.

-plantbio-

Hi plantbio,

the R² value tells you, how far away your measurements are from the "ideal line" the regression calculates. Depending on the way it is calculated, it can have different meanings. But in most cases, 0 is worst and 1 is best. You can look at it (in a linear regression) as the percentual value of the variance in your measurements that can be explained by the dilution, so an R² value of 0.89 tells you, that your measurement is very precise as it explains almost 90% of the variance (and only 11% are left for bad pipetting, degraded primers, old buffers, etc.)

The R² value is a measure of the effect size - you will often stumble upon it in all kinds of statistics...

Krümel

-krümelmonster-