True or false. (15p) a) In a cross table with r rows and c columns, the degrees of freedom equal to (r-1)(c-1). b) When testing the independence of a cross table, a valid null hypothesis is assuming that the column variable and row variable are independent. c) Chi square test can compare more than two populations. d) A "statistically significant result" usually means a low p-value for the null hypothesis. e) Outliers have no influence on the confidence intervals