With the advent of big data, data is being generated, collected, transformed, processed and analyzed at an unprecedented scale. Since data is created at a fast velocity and with a large variety, the quality of big data is far from perfect. Recent studies have shown that poor quality can bring serious erroneous data costs on the result of big data analysis. Data validation is an important process to recognize and improve data quality. In this paper, a case study that is relevant to big data quality is designed to study original big data quality, data quality dimension, data validation process and tools.