Different scales can absolutely vary, as well as your weight depending on what time of day you weigh and what you've consumed recently. I'd pick a time (early am is the best baseline) and one scale to always weigh yourself on once or twice a week, and ignore what other scales say. If i'd eaten a lot of salt during the day I can weigh 5lbs more on my home scale at night than it said i weighed in the morning. If you get different results from different scales - personally - I'd pick the most encouraging one to go with - not whichever said 15 lbs! more. Good luck!