DSE Exploratory Data Analysis Techniques 2 — Questions and Answers
Question 1: Which statistical measure is most resistant to the influence of outliers?
- Mean
- Median (Correct answer)
- Variance
- Range
Correct answer: Median
The median is resistant to outliers because it depends only on the middle value(s) of the sorted data, not the magnitude of extreme values.
Question 2: A violin plot combines features of which two visualizations?
- Histogram and scatter plot
- Box plot and kernel density estimate (Correct answer)
- Bar chart and line chart
- Heatmap and box plot
Correct answer: Box plot and kernel density estimate
A violin plot shows a box plot inside a mirrored kernel density estimate, providing both summary statistics and the full distribution shape.
Question 3: When exploring a dataset with 50 variables, which technique is most useful for quickly identifying correlated pairs?
- Scatter plot matrix
- Correlation heatmap (Correct answer)
- Pair of box plots
- Single histogram
Correct answer: Correlation heatmap
A correlation heatmap color-encodes all pairwise correlations in a compact grid, making patterns across many variables immediately visible.
Question 4: What does a Q-Q (quantile-quantile) plot primarily assess?
- Correlation between two variables
- Whether a dataset follows a theoretical distribution (Correct answer)
- The presence of outliers in a time series
- The variance across multiple groups
Correct answer: Whether a dataset follows a theoretical distribution
A Q-Q plot compares the quantiles of observed data against the quantiles of a theoretical distribution; points near the diagonal line indicate a good fit.
Question 5: Which of the following best describes 'data binning' in EDA?
- Removing duplicate records from a dataset
- Grouping continuous values into discrete intervals (Correct answer)
- Imputing missing values with the bin median
- Sorting observations by a categorical variable
Correct answer: Grouping continuous values into discrete intervals
Binning converts continuous variables into discrete categories (bins) to simplify analysis and reduce noise.
Question 6: In a right-skewed distribution, which ordering of summary statistics is correct?
- Mean < Median < Mode
- Mode < Median < Mean (Correct answer)
- Median < Mode < Mean
- Mean = Median = Mode
Correct answer: Mode < Median < Mean
In a right-skewed distribution the long tail pulls the mean up above the median, which sits above the mode.
Question 7: What is the primary purpose of jitter in a strip plot?
- To scale the axes logarithmically
- To reduce overplotting by adding small random offsets to points (Correct answer)
- To highlight outliers with a different color
- To connect observations across multiple groups
Correct answer: To reduce overplotting by adding small random offsets to points
Jitter adds small random noise to point positions so that overlapping points become distinguishable, revealing the true density of observations.
