Review the solved problems below to understand question phrasing, answer choices, and step-by-step solution logic prior to starting the full interactive practice drill:
Sample Question 1
Time-Series Forecasting & MLOps Deployment
Hard • Artificial Intelligence
In time-series analysis, what three conditions must be satisfied for a series to be considered 'Weakly Stationary' (Covariance Stationary)?
A
1. Constant mean over time, 2. Constant variance over time, 3. Autocovariance depends only on the time lag between observations and not on actual time t
B
1. Zero mean, 2. Zero variance, 3. Zero correlation
C
1. Infinite trend, 2. Extreme seasonality, 3. Random noise
D
1. Strictly positive numbers, 2. Strictly integer values, 3. Equal length intervals
✓ Correct Answer: A - 1. Constant mean over time, 2. Constant variance over time, 3. Autocovariance depends only on the time lag between observations and not on actual time t
📖 Step-by-Step Solution & Conceptual Rationale:
Stationarity ensures statistical properties do not change over time, a prerequisite for linear forecasting models like ARIMA.
Sample Question 2
Time-Series Forecasting & MLOps Deployment
Medium • Artificial Intelligence
What statistical hypothesis test is standardly used to test for the presence of a unit root (non-stationarity) in a univariate time series?
A
Augmented Dickey-Fuller (ADF) Test
B
Student's t-test
C
Chi-Square test of independence
D
ANOVA F-test
✓ Correct Answer: A - Augmented Dickey-Fuller (ADF) Test
📖 Step-by-Step Solution & Conceptual Rationale:
The ADF test checks the null hypothesis that a unit root is present (non-stationary); p-value < 0.05 rejects the null, indicating stationarity.
Sample Question 3
Time-Series Forecasting & MLOps Deployment
Medium • Artificial Intelligence
In an ARIMA(p, d, q) model, what do the parameters p, d, and q represent?
A
p = Order of the Autoregressive (AR) terms, d = Degree of differencing (Integration), q = Order of the Moving Average (MA) terms
B
p = Population, d = Density, q = Quantity
C
p = Precision, d = Dimension, q = Quantile
D
p = Penalty, d = Depth, q = Queue size
✓ Correct Answer: A - p = Order of the Autoregressive (AR) terms, d = Degree of differencing (Integration), q = Order of the Moving Average (MA) terms
📖 Step-by-Step Solution & Conceptual Rationale:
ARIMA models combine differencing 'd' to achieve stationarity with AR(p) past lags and MA(q) past forecast error terms.
Sample Question 4
Time-Series Forecasting & MLOps Deployment
Hard • Artificial Intelligence
What visual diagnostic plots are examined to determine the appropriate AR order (p) and MA order (q) in Box-Jenkins ARIMA modeling?
A
Autocorrelation Function (ACF) and Partial Autocorrelation Function (PACF) plots
B
ROC curve and Precision-Recall curve
C
Confusion matrix and Silhouette plot
D
Scatter plot and Box plot
✓ Correct Answer: A - Autocorrelation Function (ACF) and Partial Autocorrelation Function (PACF) plots
📖 Step-by-Step Solution & Conceptual Rationale:
PACF cuts off after lag p for AR(p) processes; ACF cuts off after lag q for MA(q) processes.
Sample Question 5
Time-Series Forecasting & MLOps Deployment
Medium • Artificial Intelligence
What is 'SARIMA' (Seasonal ARIMA: ARIMA(p,d,q)(P,D,Q)_s) and what does parameter 's' signify?
A
Seasonal ARIMA incorporating seasonal AR, differencing, and MA terms; 's' is the seasonal period length (e.g. s=12 for monthly data, s=24 for hourly)
B
A model for predicting summer temperatures only
C
A software tool for running ARIMA on GPUs
D
A method that ignores seasonal cycles completely
✓ Correct Answer: A - Seasonal ARIMA incorporating seasonal AR, differencing, and MA terms; 's' is the seasonal period length (e.g. s=12 for monthly data, s=24 for hourly)
📖 Step-by-Step Solution & Conceptual Rationale:
SARIMA captures both non-seasonal short-term dynamics and recurring seasonal cycle patterns (e.g. annual monsoon rainfall peaks).
Sample Question 6
Time-Series Forecasting & MLOps Deployment
Hard • Artificial Intelligence
What is 'Prophet' (developed by Meta / Facebook) additive time-series forecasting model?
A
A decomposable time-series model: y(t) = g(t) + s(t) + h(t) + epsilon_t, combining non-linear trends with changepoint detection, seasonality (Fourier series), and holiday effects
B
A religious astrology software
C
A deep learning vision model for satellite photos
D
A recurrent neural network for natural language text
✓ Correct Answer: A - A decomposable time-series model: y(t) = g(t) + s(t) + h(t) + epsilon_t, combining non-linear trends with changepoint detection, seasonality (Fourier series), and holiday effects
📖 Step-by-Step Solution & Conceptual Rationale:
Taylor & Letham designed Prophet to handle real-world business and environmental time series with missing data, trend shifts, and robust outlier handling.
Sample Question 7
Time-Series Forecasting & MLOps Deployment
Hard • Artificial Intelligence
What is 'DeepAR' (Salinas et al. / Amazon Research) for probabilistic time-series forecasting?
A
An autoregressive recurrent neural network (LSTM/GRU) that learns global non-linear representations across thousands of related time series, outputting parametric probability distributions
B
A model that only forecasts deep ocean water currents
C
A classical linear regression equation
D
A decision tree model for tabular classification
✓ Correct Answer: A - An autoregressive recurrent neural network (LSTM/GRU) that learns global non-linear representations across thousands of related time series, outputting parametric probability distributions
📖 Step-by-Step Solution & Conceptual Rationale:
DeepAR trains across large item catalogs or multi-sensor networks (e.g. 500 river gauge stations), predicting probabilistic quantile forecasts.
Sample Question 8
Time-Series Forecasting & MLOps Deployment
Hard • Artificial Intelligence
What is 'Temporal Fusion Transformer' (TFT, Lim et al. / Google Cloud AI)?
A
An attention-based architecture for multi-horizon time-series forecasting that combines Variable Selection Networks, Gated Residual Networks, and Multi-Head Self-Attention with temporal interpretability
B
A transformer that alters time in video games
C
A high-voltage electrical power transformer
D
A software tool for scheduling calendar meetings
✓ Correct Answer: A - An attention-based architecture for multi-horizon time-series forecasting that combines Variable Selection Networks, Gated Residual Networks, and Multi-Head Self-Attention with temporal interpretability
📖 Step-by-Step Solution & Conceptual Rationale:
TFT handles heterogeneous inputs (static metadata, known future inputs like rain forecasts, and observed past histories) with native prediction intervals.
Sample Question 9
Time-Series Forecasting & MLOps Deployment
Hard • Artificial Intelligence
What is 'N-BEATS' (Neural Basis Expansion Analysis for Interpretable Time Series, Oreshkin et al.)?
A
A deep neural architecture composed of backward and forward residual link blocks using basis expansions to perform pure deep learning time-series forecasting without recurrent or attention layers
B
A music rhythm generation software
C
A heartbeat monitoring device
D
A video streaming compression tool
✓ Correct Answer: A - A deep neural architecture composed of backward and forward residual link blocks using basis expansions to perform pure deep learning time-series forecasting without recurrent or attention layers
📖 Step-by-Step Solution & Conceptual Rationale:
N-BEATS surpassed classical statistical ensembles in the M4 competition by decomposing forecasts into interpretable trend and seasonality basis functions.
Sample Question 10
Time-Series Forecasting & MLOps Deployment
Hard • Artificial Intelligence
When using LSTM networks for multi-step river flood discharge forecasting, what is 'Autoregressive Multi-Step' versus 'Direct Multi-Step' forecasting?
A
Autoregressive iteratively feeds single-step predictions back as inputs for subsequent steps; Direct trains separate independent models for each future forecast horizon (t+1, t+2, ..., t+H)
B
Autoregressive runs on CPU; Direct runs on GPU
C
Autoregressive uses images; Direct uses audio
D
There is no difference in their forecasting architectures
✓ Correct Answer: A - Autoregressive iteratively feeds single-step predictions back as inputs for subsequent steps; Direct trains separate independent models for each future forecast horizon (t+1, t+2, ..., t+H)
📖 Step-by-Step Solution & Conceptual Rationale:
Direct forecasting avoids cascading error accumulation inherent in autoregressive rollouts at the cost of training H independent models.