3. In study of substance use, youth are asked how often in the past 30 days they used vapes/e-cigarettes. The choices are: 0 days, 1-2 days, 3-7 days, 8-29 days, or 30 days. What type of variable is this? a. Dichotomous b. Quantitative c. Categorical d. Ordinal 4. A matched-pairs t-test was used to examine whether patients' tumors shrink in response to chemotherapy. Tumor size was measured before and after chemotherapy. A new variable was created: delta= size_after - size_before. The sample mean of delta was -0.56 cm. Which of the following statements is true? a. On average, the tumors in the sample were larger after chemotherapy than before. b. On average, the tumors in the sample were smaller after chemotherapy than before. c. On average, the tumors in the population were larger after chemotherapy than before. d. On average, the tumors in the population were smaller after chemotherapy than before