You are a machine learning specialist for a research firm. Your team uses Amazon SageMaker and its built-in scikit-learn library for feature transformation in your machine learning process. When using the SimpleImputer transformer to replace missing values in your observations, which strategy is the default strategy that your SageMaker scikit-learn code will use if you don’t explicitly pass a strategy parameter?

Answer options:

A.constant
B.most_frequent
C.median
D.mean
E.mode

Answer: D
Option A is incorrect. The default strategy is mean. The constant strategy replaces the missing values with a constant you supply.
Option B is incorrect. The default strategy is mean. The most_frequent strategy replaces the missing values with the most frequent value along each column.
Option C is incorrect. The default strategy is mean. The median strategy replaces the missing values with the median along each column.
Option D is correct. The default strategy is mean. The mean strategy replaces the missing values with the mean along each column.
Option E is incorrect. There is no mode strategy in the SimpleImputer scikit-learn transformer.
Reference:
Please see the Amazon Machine Learning blog titled Preprocess input data before making predictions using Amazon SageMaker inference pipelines and Scikit-learn.