单元测试中出错的题目
.Suppose m=4 students have taken some class, and the class had a midterm exam and a final exam. You have collected a dataset of their scores on the two exams, which is as follows:
midterm exam (midterm exam)^2 final exam
89 7921 96
72 5184 74
94 8836 87
69 4761 78
You’d like to use polynomial regression to predict a student’s final exam score from their midterm exam score. Concretely, suppose you want to fit a model of the form hθ(x)=θ0+θ1x1+θ2x2, where x1 is the midterm score and x_2 is (midterm score)^2. Further, you plan to use both feature scaling (dividing by the “max-min”, or range, of a feature) and mean normalization.
What is the normalized feature x(4)2? (Hint: midterm = 69, final = 78 is training example 4.) Please round off your answer to two decimal places and enter in the text box below.
平均值为 (7921+5184+8836+4761)/4=6675.5
Max-Min=8836-4761=4075
(4761-6675.5)/4075=-0.46957
保留两位小数为-0.47