A professor wants to check the distribution of scores on a recent test to see if the test was too hard, too easy, or had just the right difficulty.What type of graph would be the most effective presentation?

Group of answer choices

Pie chart showing break down of letter grades

A Pareto chart sorting letter grades on the test from most frequently occurring to the least frequently occurring

Scatter plot with test grades on the x-axis and time to complete the test on the y-axis

A confidence interval with last year's test scores as the mean

Histogram with test grades grouped into classes on the x-axis