Exploratory Data Analysis Flashcards
7 cards from real MS-DS Master of Data science practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Exploratory Data Analysis flashcards as text
When computing Pearson correlation between two variables yields r = 0, what can be definitively concluded?
Answer: There is no linear relationship between the variables
Pearson r = 0 only rules out a linear association; nonlinear relationships (e.g., quadratic) can still exist with r = 0.
Which plot is BEST suited for detecting heteroscedasticity in residuals after fitting a regression model?
Answer: Residuals vs. fitted values plot
Plotting residuals against fitted values reveals fan-shaped or patterned spread, which indicates non-constant variance (heteroscedasticity).
What is the interquartile range (IQR) used to define in the standard box plot outlier rule?
Answer: The spread of the middle 50% of data used to set whisker fences
The standard Tukey rule flags points beyond Q1 − 1.5×IQR or Q3 + 1.5×IQR as outliers, where IQR = Q3 − Q1.
A dataset has 10% missing values in a predictor column. To determine whether the missingness is MCAR, MAR, or MNAR, which EDA step is most informative?
Answer: Comparing distributions of other variables between missing and non-missing groups
If other variables differ systematically between the missing and observed groups, missingness is likely MAR or MNAR rather than completely random.
In a time series EDA, a plot of autocorrelation function (ACF) shows significant spikes at lags 12, 24, and 36. What pattern does this indicate?
Answer: Annual seasonality (period = 12)
Significant ACF spikes at multiples of 12 in monthly data indicate a recurring annual seasonal pattern.
Which measure of spread is MOST appropriate when the distribution is heavily skewed?
Answer: Interquartile range
The IQR captures the spread of the central 50% of data and is resistant to the extreme values that inflate standard deviation and variance under skew.
What does a mosaic plot primarily visualize?
Answer: Association between two or more categorical variables
A mosaic plot uses tile area to represent joint frequencies, making it easy to spot deviations from independence in categorical cross-tabulations.