Not familiar with your particular stats package, but this link
explains how to test the slope of a least squares fit lit for significance. This number is almost certainly generated by your stats package
. The one I use shows the t value and the probability from that anytime you pull a least squares fit. The value of the t statistic that you find meaningful is up to you, but if you fit a line through four points, you have two degrees of freedom and
want a 95% confidence level, you need a t value of 4.3 or higher.
Test statistic. The test statistic is a t statistic (t) defined by the following equation.
t = b1 / SE
where b1 is the slope of the sample regression line, and SE is the standard error of the slope.
P-value. The P-value is the probability of observing a sample statistic as extreme as the test statistic. Since the test statistic is a t statistic, use the t Distribution Calculator to assess the probability associated with the test statistic. Use the degrees of freedom computed above.