A technology company decided to change the amount spent on marketing on the two social media sites, Tumblr and Instagram, to determine the effect on the average time on page by users. Their original strategy was to split the budget $\frac{50}{50}$ and market to both media sites equally. They switched their strategy to only spend $30\%$ of their marketing budget on Tumblr and $70\%$ on Instagram. After switching to the new strategy and collecting data for two months, they found that the average time on page decreased with the new marketing strategy.

Step $2$ of $3$: Identify the response and explanatory variables.