Alarge department store examined a sample of 18 credit card sales and recorded the amounts charged for each of three types of credit cards: mastercard, visa, and discover. six mastercard sales, seven visa, and five discover sales were recorded. the store used an anova to test if the mean sales for each credit card were equal. what are the degrees of freedom for the f statistic?
a. 3 in the numerator, 18 in the denominator
b. 18 in the numerator, 3 in the denominator
c. 6 in the numerator, 15 in the denominator
d. 2 in the numerator, 15 in the denominator