Do we have to join polygons to horizontal x-axis when there are no empty classes on sides?

Question

anonymous · Answer

Like here: I am asking about the red line

anonymous · Answer

My child, you have to plot the points in the middle of each intervals.  You have done it correctly.  So I suppose that the answer, indeed, is yes!

anonymous · Answer

So is that line colored red needed?

anonymous · Answer

I do not think that you need a constrast of colours.  The colour is completely your choice and does not make a difference.

anonymous · Answer

I colored it red so it would be easy to ask the question here. My question is do I need to extend the frequency polygon the point where both axis meet?

anonymous · Answer

Yes.  There is a reason why it is known as a polygon.

anonymous · Answer

So it is necessary to extend the frequency polygon to the point where both axes meet.  Because a polygon is closed from all sides.