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“Sentiment Analysis for Product Review using Hybrid CNN-LSTM Model”

Developed by

Nikita Tanwar

M.Sc. (Data Science) Sem-III
Savitribai Phule Pune University 2025- 2026

 

Abstract
Sentiment analysis, also known as opinion mining, has established itself as a pivotal research area in natural language processing (NLP) and machine learning due to the explosive growth of user-generated content on digital platforms. With the widespread use of online reviews, social media interactions, and other digital feedback channels, organizations and researchers alike seek automated tools to extract meaningful sentiment from large volumes of textual data efficiently and accurately. Early techniques relied heavily on traditional machine learning algorithms such as Naïve Bayes, Support Vector Machines (SVM), and Logistic Regression. While these methods can achieve acceptable performance levels, they inherently treat text as a bag of words or shallow feature vectors, which limits their ability to capture intricate linguistic nuances, semantic relationships, and long-range contextual dependencies present in natural language.

In contrast, deep learning approaches, notably Convolutional Neural Networks (CNNs) and Long Short-Term Memory (LSTM) networks, have driven significant advancements in text classification tasks, including sentiment analysis. CNNs are particularly effective at extracting local patterns and features such as n-grams and short phrase structures by applying convolutional filters, making them well suited for identifying sentiment-bearing textual fragments. On the other hand, LSTMs are designed to model sequential data and can capture long-term dependencies and contextual information through their gating mechanisms, thereby preserving the semantic flow of language over longer texts.

To leverage the complementary strengths of these architectures, this research proposes a hybrid CNN-LSTM model tailored for sentiment analysis on movie reviews. The CNN component serves as a feature extractor that identifies salient local features in the text, while the LSTM component processes these features sequentially to understand context and temporal relationships. This combined framework aims to produce a more robust and nuanced representation of sentiment by integrating spatial and temporal feature learning.

The model is implemented on the benchmark IMDB movie review dataset, a widely used corpus for evaluating sentiment classification techniques. Data preprocessing steps such as tokenization, stop-word removal, and the application of pretrained word embeddings from Word2Vec and GloVe are employed to standardize input text and imbue the model with semantic knowledge before training. The performance of the proposed hybrid model is compared against multiple baseline systems, including standalone CNN and LSTM models as well as classical machine learning classifiers, to establish empirical benchmarks.

Evaluation metrics covering accuracy, precision, recall, F1-score, and confusion matrices are utilized to provide a comprehensive assessment of classification effectiveness and error patterns. Preliminary results indicate that the hybrid CNN-LSTM outperforms baseline methods, especially in handling complex or ambiguous reviews with mixed sentiment expressions. This demonstrates the efficacy of hybrid deep learning models in achieving higher accuracy and better generalization capabilities in natural language understanding tasks.

The findings presented here contribute to the growing body of research on sentiment analysis by showing how integrating spatial and temporal neural architectures can enhance classification performance. Additionally, the research outcomes have practical implications for real-world applications such as recommendation systems, customer sentiment monitoring, social media analytics, and market research, where understanding user opinions with high precision is essential for informed decision-making.

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