Thanks for your response.
I am certainly ready to change whatever is needed to get the right result. But first, let me clarify my point.
The radii of the circles are T(alpha)*Sigma, where
T(alpha) is an alpha-quantile of the Student t-distribution,
Sigma is the group standard deviation.
Alpha is the type I error that you suggest to change if I want. I understand this. Now, suppose I have default Alpha = 0.5 and I performed the t-test on my 2 data groups and see that "Prob > t" is equal to 0.49.
If I know in advance which group is higher, and I am not interested in the situation when this group is significantly lower, I operate in one-tail test realm, and the "Prob >t" is exactly what I need. So, if this value is less than 0.5, then my groups are significantly different.
But if I click on the circles, they show no significant difference. This is because both the LSD (least significant difference) and the circles radii are calculated from the two-tailed error level equal 2*Alpha.
In my example 2*Alpha = 0.98 > 0.5
The 2-tail approach makes sense in certain situations, but my question is - can I change it to one-tail? It so happened, I do know in advance that one dataset can be only higher, and I want to test ONLY this for my error level.