http://searchenginewatch.com/article/2214161/Why-Quality-Score-is-One-of-the-Least-Important-AdWords-Metrics
It shows that QS is a reflection of the reflection of the relationship between keywords and ads, rather than the 'quality' of the landing page. In particular:
The Right Way to Improve Quality Score
If you have high cholesterol, you probably want to do something about it. And that something, if you’re smart, involves improving your lifestyle. Eating better. Exercising. And so on.
Similarly, if you suffer from low quality score, you want to do something about that as well. You want to improve the most important things about your AdWords account:
- Write compelling ads, that connect tightly to keywords, make the right promises and stand out from the rest of the search results page.
- Continually test and improve your ad copy so your ad is more likely to earn money from Google than your competitors.
- Segment your audiences so you can adjust messaging to connect with different groups’ mindsets and language.
