If you computed a chi-square value of 4.0 with a df=1, would you accept the null hypothesis? why?

No. the null hypothesis is rejected, therefore the research hypothesis is accepted. The chi square test is a non-parametric test to explain the difference between observed and expected frequencies. In order to accept the null hypothesis, the computed chi squares (column at the far right end of the table) must be smaller than the critical chi squares (two columns at the left). . By the way, what was your hypothesis about?