4. In the 2022 election cycle, Republican Blake Masters is challenging incumbent Democrat Mark Kelly to represent Arizona in the United States Senate. A recent poll of n= 627 likely voters conducted Sept. 6-7 by Emerson College* showed Kelly leading Masters 47% to 45% with a margin of error of 3.9%. We are interested in the difference in proportions of likely voters who plan to vote for Mark Kelly or Blake Masters.

What is the notation for the parameter we are estimating? Define the parameter in the context of the question.