You surely cannot describe this as "passed". With such a small sample size1. I did normality testing by GraphPad Prisms ( Kolmogorov-Smirnov test) , and both groups passed.

as n=6, even marked deviatons from normality will go unnoticed by the K-S-test.

The power of the test is very, very low with n=6. Your outlier test is much more

convincing here.

Just don't apply one-tailed tests.5. If I apply two-tailed t-test, there is no significance, no matter whether outlier is excluded or not.

Outliers distort the t-test. One question is: why does this outlierI am wondering what would be the best approach: to keep that outlier or not?

exist, which process did produce it? Was it e.g. measurement errror? Cf.

http://pareonline.net/getvn.asp?v=9&n=6 for some conceptual issues and

possible solutions.

With kind regards

K.