A lighting company seeks to study the percentage of defective glass sheels being manufactured . Theoretically, the percentage of defectives is dependent on temperature, humidity, and the level of artisan experts. Complete industrial data are available for the following variables on a daily basis for a year:
a) Temperature High, Normal, Low
b) Humidity High, Normal, low
c) Artisan expertise level Expert, Average, medium
Some experts feel that defectives also depend on production supervisors. However, data on supervisors in charge are available for only 242 of the 355 days. How should this study be conducted?