Keyword suggestion tools give vastly different results

I am really confused and want to know how to have more accurate keyword research

for example,

using DP's keyword suggestion tool it tells me that chemistry help is searched about 200 times where general chemistry is searched 1500 times

However it I use another tool it will tell me general chemistry is searched 50 times


same thing for car buying tips

one tool will suggest and tell me that used car buying tips is searched alot and then DP's will say its not searched at all.

which one do i use?

 

I think your better using a few tools to get an approximative figure of whagt you need to target.