You make a great point, Julie! Judging whether data is “good” seems to require examining the use case of the model and pre-existing circumstances that may influence decision making, both by the model and/or by humans interpreting the model. Model accuracy is definitely an important goal to optimize for, but we may also want our model to optimize for some metric of fairness, perhaps based on race and gender. Does the model treat individuals of different races or genders equally? Can we say something about the distribution of results being independent of race or gender? This notion of statistical independence may be helpful to define whether the model is fair. Because the model depends on the training data, "good" data can be defined as data that leads to a "fair" model. Perhaps, we can think of “good” meaning that the data is representative of the population that the model will be used on. For example, is the racial and gender breakdown of people in the dataset similar to the overall population? If not, the model may be biased, as Vox media producer Joss Fong illustrates in her video “Are We Automating Racism?”.