A Rewarding Summer Experience

Xiangyu Wang
·August 05, 2020

summer, I got the chance to apply some of the data science knowledge I gained in school to the real world while working as an intern at Spraoi. The opportunity to take the skills I have acquired in the classroom into the workforce and apply allows me to further explore data science, and I had a great sense of accomplishment when I saw the model we built for our client put into production to create real business values.

coming to Carnegie Mellon University for my master’s degree, I have taken various data science courses and worked on many data science projects both in a team or individually. I felt I was sufficiently prepared for the internship. But the reality is I was not. I had to continually learn and receive directions from my mentor in order to best complete this exercise.

Here are the main takeaways from this internship:

First, it takes a massive amount of experiments to find the best possible path in data science. One needs to stay creative, inquisitive, detail-oriented, and most importantly, have a huge amount of patience as the combination of technical elements from programming to tuning machine learning models can be highly complex. In our project, the data, as it comes from the real-world, is messier than I would have imagined. Not only do we have a limited amount of data, but the data itself is also highly imbalanced. To tackle this problem, I had to experiment with different sampling strategies: under-sampling, over-sampling, and sampling with different ratios, to find the training dataset that best allows the algorithm to learn enough to make the best predictions. We initially had weak model performance, using Random Forest, Decision Trees, Logistic Regression and other strategies, but the model performance was still lackluster. After researching different modeling techniques, I found that CatBoost performs exceptionally well when many categorical data columns exist. During the research process, I became familiar with some state-of-the-art algorithms in the field of data analytics which I never studied in class. Throughout the entire project process, I learned firsthand that one must have a large amount of patience to succeed in the data science field. In the journey of becoming a great data scientist, failures are inevitable, so being able to adopt a positive attitude to reframe problems multiple times is essential in searching for optimal solutions.

Second, I learned in class that for a data science project to be successful, data quality is of utmost importance and modeling performance boils down to feature engineering. At Spraoi, I experienced this for real. We were frustrated for some time because of stagnant model performance, so we had to go back to review our data and it turned out that for inactive cases, the client had not taken the time to provide us with the correct labels. After removing the problematic data, we were left with fewer data points to put in our training model, but because of the high-quality data we had in hand, the model performance was boosted. In school, I worked mostly with structured datasets. In the real world, however, data scientists typically have to analyze unstructured data a lot to obtain a good amount of information. Once we engineered some variables from the unstructured data, the model did an even better job.

Lastly, I came to realize that teamwork and communication are essential to the development of an effective data science product. Working in a team can bring in different perspectives and expertise. Increasing even a small percentage of model performance usually means a large chunk of discussion. I held regular meetings with my mentor so we could discuss and exchange our thoughts on the model. I received valuable feedback, practical advice, and general data science tips from him. Data scientists will meet bottlenecks all the time in everyday work, being in a supportive team can make all the difference.

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