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Exploratory Data Analysis Techniques Flashcards

7 cards from real DSE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which method is commonly used to detect outliers using the IQR?

    Answer: Flag values below Q1 − 1.5×IQR or above Q3 + 1.5×IQR

    The Tukey fence method flags as outliers any values more than 1.5×IQR below Q1 or above Q3, and this threshold is also used by box plots.

  2. In a pair plot (scatter plot matrix), what does the diagonal typically display?

    Answer: A histogram or KDE of each variable's distribution

    The diagonal of a pair plot shows the univariate distribution (histogram or KDE) of each variable since a scatter plot of a variable against itself is uninformative.

  3. What is the main advantage of using a KDE (Kernel Density Estimate) over a histogram for EDA?

    Answer: It produces a smooth continuous density curve that is less sensitive to bin width choices

    KDE creates a smooth density estimate that avoids the arbitrary bin-width problem of histograms, giving a clearer view of the distribution shape.

  4. You have a dataset with 10 features and want to explore relationships between all pairs. How many scatter plots would a full scatter plot matrix contain?

    Answer: 100

    A scatter plot matrix for n variables contains n² cells total, so 10×10 = 100 cells (10 diagonal + 90 off-diagonal scatter plots).

  5. Which visualization technique is specifically designed to compare distributions across multiple categorical groups simultaneously?

    Answer: Grouped box plot

    A grouped box plot displays side-by-side box plots for each category, enabling direct comparison of median, spread, and outliers across groups.

  6. What does a mosaic plot (Marimekko chart) visualize?

    Answer: The joint distribution of two or more categorical variables

    A mosaic plot tiles rectangles whose widths and heights are proportional to the marginal and conditional frequencies of two categorical variables.

  7. When you see a strong linear pattern on a scatter plot, the Pearson correlation coefficient (r) is close to which value?

    Answer: −1 or +1

    Pearson r ranges from −1 to +1; values near −1 or +1 indicate a strong linear relationship, while values near 0 indicate no linear correlation.