Final answer:
Collecting snowfall data to estimate its effect on traffic fatalities is a logical approach, but it requires careful consideration of other variables and a multivariate analysis to avoid the correlation-causation fallacy and accurately determine the true impact.
Step-by-step explanation:
The researcher's method of collecting data on snowfall in each state and adding it as a regressor to regression analyses can help estimate the effect of snow on traffic fatalities.
However, caution must be taken to ensure this does not fall into a correlation-causation fallacy. Simply because snowfall may correlate with an increase in fatalities, it does not imply causation without considering other variables such as driver error, road maintenance practices like sanding or salting, the quality of road infrastructure, and even the prevalence of all-wheel drive vehicles in a region.
Accurate estimation of the effect of snow requires a multivariate analysis that can account for these and other confounding factors. Moreover, data on snowfall must be correlated with specific incidents to confirm the hypothesis. It would also be essential to look at other weather conditions that can affect driving safety, such as freezing rain, which can impact roads differently than snow.