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.
DSE Exploratory Data Analysis Techniques 2
Which statistical measure is most resistant to the influence of outliers?