I have chemical A concentration measured at various locations from 1993-2010. I have broken the time into 2 periods 1993-2004 and 2005-2010.
How can I test whether the trend line between the two periods significantly differ?
Someone told me to use the t-test. However, I thought that the t-test is for testing differences in means between 2 population and that it does not involve trend lines. But I might be wrong.