Answer:
a. The director is wrong: the lurking variable here is the severity of the blizzard. A more severe blizzard calls for more plows and keeps people at home, where they are more likely to make online purchases.
Step-by-step explanation:
The director is correlating the number of snow plows on the road with the amount of online purchases - the correlation is high, but it doesn't mean that the increase on online purchases is caused by the number of snow plows on the road.
The question is: why would the number of snow plows on the road increase in the first place? Snow plows are sent out according to the amount of snow that has fallen, which means that the lurking variable that explains the increase in the number of snow plows and the amount of online purchases, is the severity of the blizzard in terms of how much snow has fallen. When the weather outside is too harsh or dangerous for people to go out, then it is most likely that they prefer online purchases. If the director were to analyze the correlation between the severity of the blizzard and the amount of online purchases, he would find a high correlation as well and in this case it would be the variable that actually explains the behavior of the consumers.
Remember that a lurking variable is the non-controlled variable that affects both the dependent and independent variables. In this case, there is nothing that the director can do about the severity of the blizzard besides perhaps increasing the stock whenever the severe blizzard season rolls around.