What should we do to improve the performance of the model?<br>
Although there are some choices such as getting more data, and increasing the number of features, it's not a good choice to try some ideas blindly.<br>
"Learning curve" helps us to know what is effective for the model to improve the performance.<br>
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<font color="#1E90FF"><strong>Learning curve</strong></font> is a graph that plots training scores and cross validation scores over a varying number of training instances.<br>
Learning curve tells us whether the model is in the state of "high-bias" or that of "high-variance".