What kind of chart and what version of FileMaker do you have? (charting was upgraded with the release of version 12.)
Do you want 3 bars for each week, each showing the number of records with a Good, average and Bad rating (one bar for each rating type for each week).
Or did you have some other type of chart in mind?
Note also that my question assumes that the chart will count records with one rating per record. If this is not how you have structured your data, please describe the structure that you have.