第28题: [单项选择]标准正态分布曲线下,μ±2σ的面积占总面积的() A. 80.5% B. 85.5% C. 88.5% D. 90.5% E. 95.5% 参考答案:E 答案解析:正态曲线下的面积有一定的分布规律。正态曲线总面积为1或100%,则理论上曲线下面积为:μ±1σ的面积占总面积的68.2%;μ±20的面积占总面积的95.5%;μ±3σ的面积占总面积的99.7%。
第34题: [单项选择]Passage Two Questions 29 to 31 are based on the passage you have just heard.A. Slavery. B. The fact that the North had more political power in Senate. C. Taxes. D. Different political power in the House of Representative. 参考答案:B 答案解析:[解析] Which issue did the North and the South NOT differ in