I got 15/15. I wasn't sure about a few of them, but chose the ones that looked "right" to me. I was pondering over "dumbell" vs. "dumbbell" for a while. Oddly enough, I sometimes tend to misspell some of the words differently from the misspelled choices they gave. For example, I sometimes thought that rhythm was spelled "rhythmn," liaison was spelled "liasion," and minuscule was spelled "miniscule." I'm glad those misspellings weren't included, otherwise I could have gotten them wrong.
And previously, for the longest time, I had the tendency to spell weird as "wierd," and gauge as "guage." It wasn't until after working at my current job for a while and working with pressure gauges all the time that I finally learned to spell "gauge" correctly.
There are some words which weren't included in the quiz which I still get confused in spelling, such as "inadvertent" vs. "inadvertant" and "sherbet" vs. "sherbert."
Thanks to Poneerific for Glory and Medley!