Google determines Quality Score slightly differently for each of the different advertising networks that it runs. Here we’ll learn how Quality Score is calculated for Google Search, which is the largest source of traffic for most advertisers.

　　[谷歌针对它所运营的广告网络有不同的质量分定义。本文我们将学习对于谷歌搜索来说，质量分是如何计算的]

　　According to Google:

　　Quality Score is calculated in real-time, every time your keyword matches a search query—that is, every time your keyword has the potential to trigger an ad. Quality Score is used in several different ways, including influencing your keywords’ actual cost-per-clicks (CPCs) and estimating the first page bids that you see in your account. It also partly determines if a keyword is eligible to enter the ad auction that occurs when a user enters a search query and, if it is, how high the ad will be ranked.

　　[根据谷歌的定义：每次你的关键词匹配搜索词的时候，质量分被实时计算，也就是说，每次你的关键词都有可能触发广告。质量分应用于不同的方式，包括：影响关键词实际的点击率、估算你账户中可见的第一页的竞价等。它在某种程度也决定了当一个用户进行关键词搜索的时候，你的关键词进入广告竞价的资格，如果你有资格参加竞价，它会影响广告排名的高低。]

　　What is Quality Score?

　　A Google Quality Score is a score assigned to your Google AdWords ad groups, based on a calculation of a keyword’s relevance to its associated ad text, landing page and the user’s search terms. A higher Google Quality Score leads to better ad placement (or ad ranking) at lower costs.

　　Your ad groups Quality Score is a combination of the Quality Score of each keyword you target. 

　　The following are factors that Google says go into computing the Google Quality Score.

　　（1）The historical clickthrough rate (CTR) of the keyword and the matched ad on Google.　

　　Clickthrough rate (CTR) is the number of clicks your ad receives divided by the number of times your ad is shown (impressions) via Google search only. Your ads and keywords each have their own CTRs, unique to your own campaign performance.

　　Clickthrough rate is the most significant component of Quality Score because it directly indicates which ads are most relevant to our users. For example, a well targeted keyword that shows a similarly targeted ad is more likely to have a higher CTR than a general keyword with non-specific ad text. The more your keywords and ads relate to each other and to your business, the more likely a user is to click on your ad after searching on your keyword phrase.

　　（2）The relevance of the keyword to the ads in its ad group.

　　This simply means that the keywords in your ad group must be relevant to your ads. Keywords in the ad group should be repeated in the ad text.

　　（3）The relevance of the keyword and the matched ad to the search query.

　　The keyword that a customer searches for (the search query) needs to be relevant to the keywords in your ad group and the ad itself. The match type is not taken into account when Google computes Quality Score.

　　（4）Your account history, measured by the CTR of all the ads and keywords in your account.

　　Google takes your entire history into account when determining CTR. Some advertisers have mistakenly interpreted this to mean that they should make as few adjustments to their existing keywords and ad text as possible. In fact, Google favors the recent history and give advertisers plenty of room for improvement through constant refinement. According to a posting on the Google AdWords Agency Blog’s Fact of the Day, “A few bad days of test performance will not ruin your Quality Scores. In order to optimize your clients’ accounts, we encourage you to run targeted tests on your bids, creatives, and keywords.”

　　（5）The historical CTR of the display URLs in the ad group.

　　This point refers to the URL that is displayed in the ad, not the URL that the customer is directed to after clicking the ad. This should be relevant to the keywords in your ad group.

　　（6）The quality of your landing page.

　　Google says that the three main components of a quality website are relevant and original content, transparency, and navigability.

• Relevance –Users should be able to easily find what your ad promises and the link to the page on your site should provide the most useful information about the product or service in your ad.
• Originality – Feature unique content that can‘t be found on another site. In other words, don’t mirror pages found elsewhere, and provide useful content that is relevant to your ad.
• Transparency – In order to build trust with users, your site should be explicit in three primary areas: the nature of your business; how your site interacts with a visitor‘s computer; and how you intend to use a visitor‘s personal information, if you request it.
• Navigability – Provide a short and easy path for users to purchase or receive the product or offer in your ad, avoid excessive use of pop-ups, pop-unders, and other obtrusive elements throughout your site, and make sure that your landing page loads quickly.

　　A Google crawler periodically visits your landing pages to calculate these and other usability factors.

　　Now that we’ve covered the basics on how Quality Score is calculated, let’s turn our attention back to why it’s so important.

　　From:http://www.wordstream.com/blog/ws/2010/06/09/how-quality-score-is-calculated#comments

　　Time:2014/8/29

How is Quality Score Calculated?