Can you plot a scatter diagram for grouped data?
Answers:
Hell, no!! Gave that sh*t up when I was 16!
What do you mean by "grouped data?" Do you mean grouping data points that are close together into a single value (for example, that single value may be the average of the data points.) If yes, then you can plot those average values on a scatter diagram. The usefulness of that graph depends on the validity of the algorithm used to group the data.
The main use of a scatter diagram is to try to establish whether or not there is a relationship between two sets of data. I am not sure what you mean by 'grouped data.' I would advise that you plot the individual observed or measured data pairs.
Oh, I know the answer to this, because I've done it!
In my case, the problem occured when I did a survey and wanted to plot the results as a scatter diagram. A lot of the results were the same. For example, lots of the people answered 3 to the first question and 5 to the second question. If I simply plotted their answers on the graph, I would end up with just one point on the graph. To get round this, I added a small random amount to each of the values. That way, the spreadsheet plotted them all separately.
You could use the same method for grouped data. First 'expand' the grouped data into separate entries. For example, if you have 11 results at the grouped point (3,5) then turn that into 11 separate entries of (3,5). Then add a small random perturbation to each of the data items, and plot them.
As others have said, it is better to plot the raw ungrouped data, but if you cannot do that for some reason then this is the next best thing.
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