Answer:
The option B calculates the standard deviation of variables Exam1 and Exam4.
Explanation:
First, let's write the first two lines correctly:
- import pandas as pd
- scores = pd.read_csv('ExamScores.csv')
Now, let's analyse each option:
- The option A is incorrect
The expression std[['Exam1','Exam4']] is the incorrect part because in this case std is working as a variable and the std was not previously declared. So it will generate an error.
- The option C is incorrect
The expression std[['Exam1','Exam4']].scores() is incorrect because of two reasons: first, std is working as a variable and the std was not previously declared (as in option A), second, .scores() is working as a method and in this case, scores is the variable. So it will generate an error.
- The option D is incorrect
The expression [['Exam1']] is the incorrect part because it doesn't include the 'Exam4' and the problem is asking for the standard deviation of variables Exam1 and Exam4.
- The option B is CORRECT
The expression std[['Exam1','Exam4']] refers to the variables Exam1 and Exam4 from the total exams. As scores is a pandas variable and .std() is a method provided by pandas library, the expression .std() allows to get the deviation standard of the variables Exam1 and Exam4.
Thus, the option B calculates the standard deviation of variables Exam1 and Exam4.
