e-rater是什么？e-rater打分机制说明

不是什么内部机密，都是ETS自己的官网公布的东西。

明白了这些机理以后，相信不管是口语还是写作，拿个高分，你应该就会比较有信心了。

当然就像课上反复强调了，了解怎么打分，只是指明了一个明确的方向，当有了方向以后，剩下的就是练习了。

首先说下TOEFL 写作的阅卷操作，内容来自于ETS研究员 Catherine S. Trapani 的一篇关于e-rater 的报告。

对于不了解e-rater 的首先和大家简单介绍下这个软件

# 关于e-rater

e-rater 是 ETS 研发的一个自动打分软件 （automated scoring model）。在 TOEFL 的写作，GRE 的写作和GMAT 的写作部分里面都有应用。

目前TOEFL 的写作部分的打分机制是，一位 human-rater  和 e-rater 打分，最终成绩是两个加起来的平均分。当然如果两个的分值相差过大，会有第二个human-rater 来打分。

E-rater’s use was investigated as a contributory score. Under the contributory score model, e-rater score was checked for agreement with the first human score within an empirically established range, beyond which a second human score was required. The average of the human and e-rater scores became the final score for the essay, unless a second human rating was desired.

另外要注意的是e-rater 的阅卷是模仿人的打分方式，所以通过e-rater 的打分机制，可以很好的知道，整个写作部分到底是怎么打分的。

# e-rater 打分机制

这张图非常的关键，可以看出e-rater 的打分大体分成几个角度

1. organization

2.development

3. positive features

4. grammar

5. usage

6. mechanics

7. style

...

当然这么多内容，第一个问题：

这些名词到底是什么意思？？？

我们用paper 中的一段话来简单地介绍下上面几个概念。

Grammar, usage, mechanics, and style together identify over 30 error types, including errors in subject-verb agreement, homophone errors, misspelling, and overuse of vocabulary. These error types are summarized for each feature as proportions of error rates relative to the essay length. Organization and development features are based on automatically identifying sentences in an essay as they correspond to essay-discourse categories: introductory material (background), thesis, main ideas, supporting ideas, and conclusion. For the organization feature, e-rater identifies the number of elements present for each category of discourse in an essay. For the development feature, e-rater computes the average length for all the discourse elements (in words) in an essay. Lexical complexity of the essay is represented by two features. The first is computed through a word frequency index used to obtain a measure of vocabulary level. The second feature computes average word length across all words in the essay and uses this as an index of sophistication of word usage. A new feature indicative of correct use of collocation and preposition use in the essay was the first feature to be included in e-rater version 10.1 to support further development of measures of positive attributes of writing style and ability (Ramineni, Davey, & Weng, 2010).

第二个问题，他们的重要程度是一样的吗？？？

用 Catherine S. Trapani 在一个学术会议上的slide 来回答这个问题

你可以看到 Organization 和 development 的权重相对是比较高的。而有上面的定义你看到的

Organization 是the number of elements present for each category of discourse in an essay

Development 是e-rater computes the average length for all the discourse elements (in words) in an essay

所以，如果你明白了提分的关键，接下来就去多写就好。