The researcher's null hypothesis isH₀:²= 420. A sample ofn= 18 items yields a sample variance ofs²= 512. Thecritical valuesof chi-square for a two-tailed test at= .05 are:

8.672 and 27.59

7.564 and 30.19

-1.960 and +1.960

9.390 and 28.87