Here's a useful question that someone asked me:
Is it a good idea to use statistical terms such as linear / exponential growth instead of more general phrases like gradual / significant increase?
My answer is no. I don't advise you to write about linear or exponential growth in writing task 1. You are not expected to have any technical knowledge of statistics in this task, and so this kind of "statistics language" seems a little forced and inappropriate to me.
Just use the 'normal' phrases that I use in my example answers here on the blog. Don't try to write like a professional statistician, and don't use the exaggerated language that I mentioned in this lesson.