The table below gives beverage preferences for random samples of teens and adults.
teens adults total
coffee 50 200 250
tea 100 150 250
soft drinks 200 200 400
other 50 50 100
400 600 1000
We are asked to test for independence between age (i.e., adult and teen) and drink preferences. With a .05 level of significance, the critical value for the test is?
a. 1.645
b. 7.815
c. 14.067
d. 15.507