1NAMILL,

You can look up the critical value from the chi-square table, under row df=3-1=2 and column chi-square(0.95). If this is for a 95% confidence interval then you should get chi-square(2, 0.975).

1.96 is Z(0.975) from normal table, it's for a 95% confidence interval. Notice confidence interval is different from confidence level.