Yes, if 2015 was the 6th year of your residency in the USA under an F-1 visa as a international student, you will not longer be exempt from the Substantial
Presence Test (SPT) and will be considered a US resident for 2015.
Please refer to this US Tax Guide for Aliens for additional information about visa exemptions
and the various filing requirements.
Your change in degree plan will not affect whether or not you are considered a resident alien for US income tax purposes.
