NO.PZ202109130200004301
问题如下：
Based on Exhibits 1 and 2, if Liu were to graph the 50 observations, the scatter plot summarizing this relation would be best described as:
选项：
A.horizontal B.upward sloping C.downward sloping解释：
C is correct. The slope coefficient (shown in Exhibit 2) is negative. We could also determine this by looking at the cross-product (Exhibit 1), which is negative.
表格一最后的结果应该是协方差吧？
通过协方差是负数可以直接判断出来是负相关么？
