DSE Basic 5 — Questions and Answers
Question 1: What is the difference between structured and unstructured data?
- Structured data is larger; unstructured is smaller
- Structured data fits in predefined schemas; unstructured does not (Correct answer)
- Structured data is always numerical; unstructured is always text
- There is no real difference
Correct answer: Structured data fits in predefined schemas; unstructured does not
Structured data is organized in predefined schemas (like tables), while unstructured data lacks a fixed format (like images or emails).
Question 2: Which sampling method gives every member of the population an equal chance of being selected?
- Stratified sampling
- Cluster sampling
- Simple random sampling (Correct answer)
- Convenience sampling
Correct answer: Simple random sampling
Simple random sampling ensures every individual has an equal probability of selection, minimizing selection bias.
Question 3: What is a confusion matrix used for?
- Visualizing correlations between features
- Evaluating classification model performance (Correct answer)
- Detecting outliers in data
- Tuning hyperparameters
Correct answer: Evaluating classification model performance
A confusion matrix shows counts of true positives, false positives, true negatives, and false negatives for a classifier.
Question 4: Which of the following algorithms is used for dimensionality reduction?
- K-Nearest Neighbors
- Principal Component Analysis (PCA) (Correct answer)
- Random Forest
- Logistic Regression
Correct answer: Principal Component Analysis (PCA)
PCA projects high-dimensional data onto fewer principal components that capture the most variance.
Question 5: In data science, what is a 'data lake'?
- A structured relational database
- A centralized repository storing raw data in any format at scale (Correct answer)
- A type of visualization tool
- A machine learning framework
Correct answer: A centralized repository storing raw data in any format at scale
A data lake stores raw, unprocessed data in any format at scale, unlike a data warehouse which stores structured, processed data.
Question 6: What does a p-value less than 0.05 typically indicate?
- The null hypothesis is true
- The result is statistically significant at the 5% level (Correct answer)
- The effect size is large
- The sample size is too small
Correct answer: The result is statistically significant at the 5% level
A p-value < 0.05 means there is less than a 5% chance of observing results this extreme if the null hypothesis were true.
Question 7: Which of the following best describes 'data wrangling'?
- Building predictive models
- Cleaning and transforming raw data into a usable format (Correct answer)
- Deploying models to production
- Creating data visualizations
Correct answer: Cleaning and transforming raw data into a usable format
Data wrangling (also called data munging) involves cleaning, restructuring, and enriching raw data to make it analysis-ready.
DSE Basic 5
What is the difference between structured and unstructured data?