Graded Quiz: Advanced CNNs in Keras :Deep Learning with Keras and Tensorflow (IBM AI Engineering Professional Certificate) Answers 2025
1. Question 1
Architecture that uses small 3×3 filters and increases network depth:
-
❌ GRU
-
❌ RNN
-
❌ LSTM
-
✅ VGG
Explanation:
VGG16/VGG19 use repeat blocks of 3×3 convolutions to form deep CNNs.
2. Question 2
Purpose of MaxPooling2D((2,2))?
-
✅ Reduces dimensionality
-
❌ Flattens feature maps
-
❌ Final classification
-
❌ Extracts features
Explanation:
MaxPooling reduces spatial size, computation, and helps retain dominant features.
3. Question 3
How ImageDataGenerator helps in augmentation?
-
❌ Reducing resolution
-
❌ Cropping only
-
❌ Adding noise
-
✅ Rotating, shifting, flipping images
Explanation:
ImageDataGenerator creates varied images to reduce overfitting.
4. Question 4
Purpose of featurewise_center?
-
❌ Normalize each sample individually
-
✅ Set the dataset’s mean to 0
-
❌ Rotate images
-
❌ Add noise
Explanation:
featurewise_center subtracts the global dataset mean from all images.
5. Question 5
Common ImageNet pre-trained model for transfer learning?
-
❌ RNN
-
❌ GRU
-
✅ VGG16
-
❌ LSTM
Explanation:
VGG16 is a classic CNN widely used for transfer learning.
6. Question 6
Meaning of include_top=False?
-
❌ Exclude batch norm
-
❌ Exclude pooling layers
-
❌ Exclude convolution layers
-
✅ Exclude fully connected (classification) layers
Explanation:
This keeps the convolutional base but removes the dense classifier.
7. Question 7
Why freeze pre-trained model layers initially?
-
❌ Speed up training (secondary effect)
-
✅ Keep pre-trained weights unchanged
-
❌ Reduce memory
-
❌ Prevent overfitting
Explanation:
Freezing preserves learned features from ImageNet.
8. Question 8
Fine-tuning a pre-trained model means:
-
❌ Freeze all layers
-
❌ Train only top layers
-
❌ Change architecture
-
✅ Unfreeze and retrain some deeper layers
Explanation:
You refine higher-level feature representations.
9. Question 9
Role of flow_from_directory?
-
✅ Load images + apply augmentation from directory
-
❌ Generate synthetic images
-
❌ Convert to grayscale
-
❌ Compile model
Explanation:
It loads batches of images directly from folders.
10. Question 10
How does transpose convolution upsample images?
-
❌ Compile with Adam
-
❌ Downsampling
-
❌ Simplify architecture
-
✅ Inserting zeros between elements of the feature map
Explanation:
Transpose convolution performs learnable upsampling via zero-insertion + convolution.
🧾 Summary Table
| Q# | Correct Answer |
|---|---|
| 1 | VGG |
| 2 | Reduces dimensionality |
| 3 | Rotating, shifting, flipping |
| 4 | Set dataset mean to 0 |
| 5 | VGG16 |
| 6 | Exclude top fully connected layers |
| 7 | Keep pretrained weights unchanged |
| 8 | Unfreeze and retrain layers |
| 9 | Load images & augment |
| 10 | Insert zeros (transpose conv) |