Data Science Study Guide 2026
Everything you need to pass the Data Science exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 Data Science Exam Format at a Glance
📚 Data Science Topics to Study (103)
✍️ Sample Data Science Questions & Answers
1. What is multicollinearity in a regression model?
Multicollinearity occurs when independent variables are highly correlated with each other.
2. When splitting data into training and test sets, why should stratified sampling be used for imbalanced classification problems?
Stratified sampling preserves the original class proportions in both splits, preventing situations where the minority class is underrepresented or absent in one set.
3. Combining two DataFrames on a shared key column in pandas is done with:
pd.merge joins DataFrames on common key columns.
4. When you send a MapReduce task to a Hadoop cluster, you discover that even though it was sent successfully, the job has not yet been finished. What ought you to do?
In older Hadoop 1.x architectures, the TaskTracker was responsible for executing individual Map and Reduce tasks on the data nodes. If a MapReduce job has been successfully sent but is not finishing, it indicates that the tasks themselves are not being executed. Therefore, ensuring the TaskTracker (or its equivalent, the NodeManager in Hadoop 2.x+) is running is crucial for job execution.
5. Which dimensionality reduction technique is unsupervised and linear?
PCA is an unsupervised, linear method that projects data onto directions of maximum variance.
6. Which type of data visualization is best suited for showing the distribution of a single continuous variable?
Histograms display the frequency distribution of continuous data by grouping values into bins and showing their counts.