单选题
An analyst does research about correlations and gathered information about three economic variables. He noted that whenever variable X increased by one unit, variable Y increased by 0.5 units but variable Z decreased by 0.5 units. The correlation between variables X and Y and the correlation between-variables X and Z, respectively, are closest to:
【正确答案】
C
【答案解析】[解析] X和Y是完全正相关(相关系数为1)，因为X上升1个单位，Y总是上升0.5个单位；而X和Z是完全负相关(相关系数为-1)，因为X上升1个单位，Y总是下降0.5个单位。题目中要注意相关系数和斜率的关系。