Alarge department store examined a sample of the 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 denominatorb. 18 in the numerator, 3 in the denominatorc. 6 in the numerator, 15 in the denominatord. 2 in the numerator, 15 in the denominator