I am trying to understand analysis in a paper which talks about statistical significance of a certain stimulus. I have used 'VALUE' in place of the specific variable that is being observed, and 'STIMULUS' to represent experimental stimulus on the experiment group that may influence the VALUE people get. The following is what it says:
We ﬁnd that 89% of those who got their VALUE increased were given the STIMULUS (experiment group), compared to 64% who did not get the VALUE increased. This diﬀerence is signiﬁcant (p=.000065, χ2=16.02), and suggests that STIMULUS impacts the VALUE people get.
I would like to understand how the author has calculated the significance. What kind of significance test is this?