中误差
参考答案：
是一个描述测量精度的指标，指的是在相同观测条件下对同一未知量进行n次观测，所得各个真误差平方和的平均值，再取其平方根，称为中误差。
单句改错：找出错误的一项并改正。
( )1. Sandy was one of the model at the fashion show. ______
A B C D
( )2. Sandy wore her hair in a 1990's style last Friday. ______
( )3. Miss Hu came into the classroom and the students stopped to talk. ______
( )4. Simon often takes Amy to home and they play the piano together. ______
( )5. There are at least three thousands students in our school. ______
从政府制定政策的角度，提出解决给定资料所反映问题的对策建议。要求：有针对性，有条理，切实可行。字数不超过350字。
