Acceptability of linearity data is often judged by examining the correlation coefficient and y-intercept of the linear regression line for the response versus concentration plot.

I have found in some papers these type of criteria:

1. The y-intercept should be included in the confidence interval (p=95%) around zero.

2. The y-intercept should be less than a few percent of the response obtained for the analyte at the target level.

My question is what must I understanding by "few %", and witch is the relation between these two criteria.