Maths Histograms_1

Maths Histograms_1

1. Area = frequency

2. area of bar represents frequency, bars with same area represent same frequency

3. Completing histograms. 2 methods

   • Frequency density method
     • Area = frequency, so if have frequency you have area. Therefore to get frequency density you do area divide by the number on the other column. Or if you have the frequency density but not the density then times the frequency density with the number from the other column.
       • Then go to the bar and go to the height and label it what ever number you got. You now have a scale to do the rest.
     • This method = more useful when have a graph with tiny squares
   • 1st of all with both methods, choose row with bar and frequency
   • Square method
     • How many people is a square worth?
       • Go to bar that also has the frequency and count how many squares are in that bar. Then do a quick sum. E.g if you know the frequency is 8 and you have counted 4 squares in the bar then do 4 SQUARES = 8 UNITS, So to get one square divide by 4, therefore 1 square = 2 units
         • Now you know how many squares is worth, count all the squares in the bars and and times them by whatever the unit is to 1 square (in example below 1 square = 2 units, so would times squares by 2 to get frequency.
           • If have frequency and not not squares, then to get squares just divide frequency by unit of 1 square. (in example before 1 square = 2 units, so times frequency by 2 to get the number of squares then draw the graph.

4. In some questions you may need to shade areas then add all shaded area up together to get answer, whether it be find percentage of.., estimate number of...below.... etc

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