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请根据教材第四课课文(三)“这些T恤衫是新款的”课文内容，试论述这些T恤衫是新款的，具体表现在哪里。
请根据教材第四课课文（三)“这些T恤衫是新款的”课文内容，试论述这些T恤衫是新款的，具体表现在哪里。
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更多“请根据教材第四课课文(三)“这些T恤衫是新款的”课文内容，试…”相关的问题
(i)你为什么会把这些数据归类为聚类样本？大致上，你预期能从一个典型学生得到大概多少次观测？
(ii)写出一个类似于教材方程(14.12)那样的模型，用到课率和其他特征去解释期终考试成绩。以s作为学生下标和c作为课程下标，对同一个学生哪个变量是不变的？
(iii)如果你把所有的数据混合起来并使用OLS，那么，对影响成绩和到课率的非观测学生特征，你正在做什么假定呢？SAT和学期前GPA在这方面扮演着什么角色呢？
(iv)如果你认为SAT和学期前GPA不足以刻画学生能力，你如何估计到课率对期终考试成绩的影响呢？
参考答案：
6.利用计量经济软件
中的“聚类”选项，便得到教材表14-2中混合OLS估计值充分稳健[即对复合误差(vit：t=1，···，T)中的序列相关和异方差性保持稳健]的标准误为：
(i)这些标准误与非稳健标准误相比一般如何？为什么？
(ii)混合OLS的稳健标准误与RE的标准误相比如何？解释变量是否随时间变化有什么关系吗？
PASSAGE 1 (教材课文原文)
With a teeny waist, exaggerated breasts, icy-blue eyes, 21-year-old Valeria says she is the real natural deal. A real-life Barbie, that is.
That’s what she claims anyway, but many people doubt to her claims. Whether she underwent plastic surgery or uses Photoshop remains unclear. On her blog, the model notes that she is the most famous woman on the Russian Internet because of her doll-like appeal. Hundreds of photos on her Facebook page show a wide-eyed, nearly fake-looking Valeria posing in a variety of outfits.
The model did not return requests for comment. If Photoshop is not a factor in getting Valeria’s look, she likely underwent a barrage of plastic surgery. The president of American Society of Plastic Surgeons (ASPS)said, plastic surgery should never be used to transform. oneself into a favorite celebrity or, in this case, a play toy. He also warns patients to keep in mind that plastic surgery is real surgery with real risks, just as with any operation, so the decision should not be taken lightly.
1. Valeria thinks that she is a real-life Barbie.{T; F}
2. Valeria used to accept plastic surgery.{T; F}
3. Valeria writes that she is the most famous woman on the Russian Internet because she posts a lot of pictures on her blog..{T; F}
4. The author thinks Valeria neither Photoshops her, nor accepts a series of plastic surgery.{T; F}
5. The president of ASPS thinks that plastic surgery is of risks.{T; F}
PASSAGE 1 (教材课文原文)
"The printer did not always manage to spread the plastic evenly, making some of the ribs of the honeycomb structure of the block uneven," reported ARN (Australian Radio Network) to the surprise of no one who has used a 3D printer. But the architects remain optimistic. The first few printed blocks are meant to be test pieces as they improve the process.
It takes about a week to print a 3-meter high block right now. The project's leaders hope to eventually get that down to two hours and finish the first of 12 rooms in a year, and the entire house in less than 3 years.
Ultimately, 3D Print Canal House is an architectural research project, one that is very much being conducted in the public eye: you can actually buy tickets to visit the construction site for 2.50 Euros.
The top floors will become more ornate, for example, as newer techniques are incorporated. They'll explore the possibilities of 3D printing, like the honeycomb walls or an entire room recycled, redesigned, and built anew. Nobody's going to move into a 3D printed house soon, but, if anyone ever does, something might be learned from this experiment by the canal.
1. According to the passage, the 3D printer can type with plastic evenly.{T; F}
2. This 3D printer printed some blocks to test its work.{T; F}
3. The project's leaders will finish the entire house in less than 3 years.{T; F}
4. 3D Print Canal House is printed to live.{T; F}
5. The canal house will be decorated more.{T; F}
