SOFTWARE ENGINEER & SDET

Jennifer Montgomery

Backend · full-stack · quality engineering

COURSEWORK / RECELL

Supervised learning with linear regression

Which device attributes help explain the resale price of a used phone or tablet?

← Coursework on resume

Completed UT Austin postgraduate coursework using a supplied scenario, dataset, and starter notebook. The charts below come from my completed notebook.

SUPERVISED LEARNING

ReCell

COURSE FOCUS

Regression, feature selection, and model assumptions

LIBRARIES USED

pandas, NumPy, statsmodels, scikit-learn, Seaborn, Matplotlib

The supplied data

The course provided 2021 used and refurbished device records. Predictors included brand, operating system, screen size, camera resolution, memory, battery, release year, days used, and normalized new-device price. The response was normalized used-device price; the analysis concerns that transformed price, not a live resale quote.

What I did

  • Explored price distributions, brand and operating-system representation, and relationships among numeric features.
  • Built an ordinary least squares regression model, compared train and test errors, and reduced predictors using significance and variance inflation checks.
  • Reviewed residual plots and tests for linearity, normality, and constant variance before interpreting the final model.
Scatterplot of normalized new-device price against normalized used-device price, showing a strong positive association.
From the notebook: devices with higher normalized new prices tended to have higher normalized used prices in this dataset. Open chart ↗
Correlation heatmap for device dimensions, camera, memory, battery, new price, and used price.
From the notebook: correlation screening informed the regression work; correlation alone does not establish an independent effect. Open chart ↗

Finding in the course model

Normalized new-device price was strongly associated with normalized used price. The final model had adjusted R² of about 0.836, with comparable training and test errors in the notebook. Camera resolution, RAM, release year, screen size, and new price remained useful model features.

Learning reinforced

This exercise connected exploratory correlation to a multivariable model, then tested whether the model’s assumptions and held-out errors supported its interpretation. The dataset’s operating-system mix was heavily Android, a limitation when generalizing to other devices.