Final answer:
A class interval is a range of values used to group data in histograms. Class boundaries are the upper and lower limits of each interval. Class size is the difference between the upper and lower class limits. Class marks are the average values of each interval.
Step-by-step explanation:
A class interval or interval is a range of values in a set of data. It is used to organize and group data when creating histograms or frequency tables.
Class boundaries or class limits are the values that define the upper and lower limits of each class interval. They are calculated by subtracting or adding half of the class size to the lower and upper class limits, respectively.
Class size or width is the difference between the upper and lower class limits. It determines the range of values that are included in each class interval.
Class marks or midpoints are the values that represent the center of each class interval. They are calculated by finding the average of the lower and upper class limits.