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Step by Step Guide to Constructing Ogives

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Step by Step Guide to Constructing Ogives

  1. 1. Ogives Year 8 ECHO Mathematics
  2. 2. Introduction  An ogive is a way to graph information showing cumulative frequencies.  Your vertical scale will represent cumulative frequencies and your horizontal scale will represent upper class/interval boundaries.  Ogives always start at the left with a cumulative frequency of zero at the lower class boundary of the first class.  The ogive should end on the right with the cumulative frequency equal to the sample size at the upper class boundary of the last class.
  3. 3. Example one: The following data consists of weights, in kilograms, of 20 people: 50, 65, 75, 80, 85, 85, 86, 86, 87, 87, 87, 90, 92, 98, 105. Placing this data into a stem and leaf plot helps us organise and analyse and group our data better. This is not a necessary step. Step 1: Group your data into the table. Stem Tally Leaf 5 0 6 5 40<weights<50 7 5 50<weights<60 8 0, 5, 5, 6, 6, 7, 7, 7 9 0, 2, 8 10 5 60<weights<70 70<weights<80 80<weights<90 90<weights<100 100<weights<110 Frequency Cumulative Frequency
  4. 4. Step 2: Put your data into the table (Start with tallies) Stem Leaf 5 0 6 5 7 5 8 0, 5, 5, 6, 6, 7, 7, 7 9 0, 2, 8 10 5
  5. 5. Step 3: Put the frequencies by which the events occurred. Stem Leaf 5 0 6 5 7 5 8 0, 5, 5, 6, 6, 7, 7, 7 9 0, 2, 8 10 5
  6. 6. Step 4: Put in the cumulative frequency totals Stem Leaf 5 0 6 5 7 5 8 0, 5, 5, 6, 6, 7, 7, 7 9 0, 2, 8 10 5
  7. 7. Step 5: Draw your graph • The first coordinate in the plot always starts at a value of 0 • The second coordinate is at the end of the first interval. • The third coordinate is at the end of the second interval and so on.

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