If you think that is how science is done, you probably need to go back to watching lady gaga and let the adults talk.
Here is what the real study would be. People notice lung cancer incidents are on the rise and people with cancer admit to being smokers. Someone analyzes the data and draws the correlation between people with lung cancer and smoking. They find a connection in the data and make policy accordingly. Someone gets a hold of the data and does their own analysis and says Yep, they are right or no they are wrong.
But here is some interesting facts for you that make smoking and cancer not as cut and dry as you think it is. In today's pop culture, it seems it is a given that if you smoke you will get cancer. "Fewer than 10 percent of lifelong smokers will get lung cancer". "In the game of risk, you're more likely to have a condom break than to get cancer from smoking." but from an analysis perspective " Smoking accounts for 30 percent of all cancer deaths and 87 percent of lung cancer deaths; the risk of developing lung cancer is about 23 times higher in male smokers compared to non-smokers; smoking is associated with increased risk of at least 15 types of cancer".
So lets stop pretending that something like smoking and cancer is so obvious that the tobacco company's denials were baseless.