how to draw two tailed t test .....

I want to draw picture like FIG1.(a) .

This paper said that calculations were based on a two-sided student's t-test with the effective degrees of freedom estimated by considering serial autocorrelation of data.

please tell me .... how to draw dots like FIG (a)..

[John D'Errico]

Please don't post repeat questions just to add information to the first one.