""

The authors admit this in the paper. They write: "This is a cross-sectional study, which only allows us to identify associations, not causal relationships."

Finally, while it is true that the typical RCT is limited because it does not simulate the real-life situation where smokers can choose between different products, change products over time, and engage in social networks to support their vaping, the study we had proposed would have allowed for all of these things. We would have given smokers a wide range of products to choose from and allowed them to experiment with different products and make changes if they desired, and we would have referred them to a number of vaping web sites and support groups. In fact, we had decided to include a training and information session with an actual vaper as part of the study. This would still not have simulated the real-life situation exactly, but it would have significantly helped to make the study more meaningful by making it more similar to what happens in "real life."

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