Solved – Two Sample t-test gives p-value of zero

t-test

I have two data sets, both are normally distributed (p<0.05). When I run a two sample t-test to assess if there is a significant difference between the means, I get a p-value of exactly zero?

What does this mean? I have never encountered it before. Below is the output from Minitab for the test.

Thank you all for your time.
Regards,
Tom

Two-sample T for 50_0.22 vs 50_0.12

           N    Mean  StDev  SE Mean
50_0.22  4709  1.48   1.48    0.022

50_0.12  4709  1.23   1.00    0.015


Difference = μ (50_0.22) - μ (50_0.12)
Estimate for difference:  0.2477
95% CI for difference:  (0.1967, 0.2986)
T-Test of difference = 0 (vs ≠): T-Value = 9.53  P-Value = 0.000  DF = 8286

Best Answer

The p-value is not really 0, it's just being reported as 0 in that output because it's being rounded down and it looks like the output can only display 3 digits after the decimal.

Related Question