Critics of my recent blog post Trump’s Tariffs: What Economists Get Wrong correctly pointed out that my claim of improved economic performance under Trump wasn’t convincing since the economy also grew over the last few years of the Obama Presidency.

Here’s an analysis showing statistically significant improvement in GDP growth during the Trump presidency versus the last couple of years under Obama. You can read more about the factors contributing to this growth here.

First, I collected the following data from the US Bureau of Economic Analysis.

Year	Quarter	GDP % Growth Rate	President
2014	Q4	1.9	Obama
2015	Q1	3.3	Obama
2015	Q2	3.3	Obama
2015	Q3	1.0	Obama
2015	Q4	0.4	Obama
2016	Q1	1.5	Obama
2016	Q2	2.3	Obama
2016	Q3	1.9	Obama
2016	Q4	1.8	Obama
2017	Q1	1.8	Trump
2017	Q2	3.0	Trump
2017	Q3	2.8	Trump
2017	Q4	2.3	Trump
2018	Q1	2.2	Trump
2018	Q2	4.2	Trump
2018	Q3	3.4	Trump

Then, I used the “t-Test: Paired Two Sample for Means” Function in Excel’s Data Analysis Toolpak to determine there’s a greater than 95% probability that there’s a statistically significant significant improvement in GDP growth during the time Trump has been president. I display the results of this statistical test below.

Statistic	Obama	Trump
Mean	1.74%	2.81%
Observations	7	7
Hypothesized Mean Difference	0
P(T<=t) one-tail	4.84%

I assumed a Null Hypothesis that there was no difference in means. The t-test shows there’s a 4.84% probability that this hypothesis is correct. Meaning, there’s a 95.16% (100% – 4.84%) probability that the mean and the two populations of GDP Growth are different.