FAQ/bar - CBU statistics Wiki

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If a rating scale has a category which doesn’t occur e.g. ‘Very Unimportant’ this category is not shown in the bar charts. This can be a disadvantage for example in checking for Normality or even getting an impression of the complete range of possible data values. This can be overcome by weighting the cases.

Example…. Let’s suppose we wish to graph group frequencies, held in a single column of raw (individual) data (FDAT), on a simple bar graph in SPSS. One or more of the groups doesn’t occur. The following procedure will produce the complete bar chart.

  1. Add dummy ratings representing those which have not occurred to FDAT.
  2. Construct a weight variable (WVAR) which takes the value ‘1’ for all ratings which occur and some very small positive weight for the dummy cases e.g. 0.001.
  3. Got to Data:Weight Cases and place WVAR in the weight cases by box.

  4. Go to Graphs: Bar: Simple and input the categorical variable.

You should now have a space on the x axis allocated for all possible ratings.

  • You could do this inputting total frequency for each bar graph level using the method above. WVAR would now represent the frequency per level with 0.001, as before, used for non-occurring levels.