Math Is Fun Forum

EbenezerSon

Member

Registered: 2013-07-04

Posts: 554

How to count decimals on graph axis

Hi everyone;

I'm dealing with graph problems with the class boundaries on the horizontal axis against the cummulative frequency on the vertical axis. The upper class boundary on the horizontal axis reads;
9.5,  19.5,  29.5, 39.5,  49.5,  59.5,  69.5,  79.5, 89.5,  99.5...

The above decimals are on the deepend perpendicular lines of the horizonal lines.
How are you going to count using the thin lines on the graph from one decimal to another?
I tried counting by saying 9.5 then to 10.5 then to 11.5 then to 12.5 then to 13.5 is the counting correct?

Last edited by EbenezerSon (2016-02-22 04:29:14)

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I know only one thing - that is that I know nothing

Bob

Administrator

Registered: 2010-06-20

Posts: 10,619

Re: How to count decimals on graph axis

hi EbenezerSon

Class boundaries have to be defined so that a value is in only one class.  Thus 0.5 ≤ x < 1.0 for example, rather than 0.5 ≤ x ≤ 1.0

By their nature cumulative frequency graphs are really discrete but it is usual to create a continuous curve as if there were a continuum of values.  It seems reasonable to do as you suggest but you are right to question it.  Here's a example where it would not be right at all to assume a continuous x axis.  Suppose we put out a rain fall pot and leave it for a month.  Then we record the total rainfall for that month and empty the pot, ready to collect the next month's rainfall.  You could make a graph with the collected values up the side and the months across the bottom.  You could certainly use this to show which months are heavy with rain and which are low.  But you could not join the points and interpolate the rainfall for say 15th April.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob