When examining an association in which one variable is categorical and one is quantitative, a scatterplot is NOT likely to be used.
A scatterplot is a graph that displays the relationship between two quantitative variables, where each point on the graph represents a pair of values for the two variables. In an association between a categorical variable and a quantitative variable, a scatterplot would not be appropriate because the categorical variable cannot be represented on a continuous scale.
Instead, a bar graph is typically used to display the relationship between a categorical variable and a quantitative variable. The bar graph shows the mean or median value of the quantitative variable for each category of the categorical variable, with the height of each bar indicating the value.
A correlation can be used to measure the strength and direction of the association between the two variables, but it does not provide information about the differences between groups or categories.
A t-test can be used to compare the means of the quantitative variable between two groups defined by the categorical variable, but it does not provide information about the association or relationship between the two variables.
Therefore, the correct answer is 1. A scatterplot.