Here is a more Mathematica-like approach to what I think you are looking for. Note that it is not using procedural constructs, and studiously avoids the Print statement. But I'd also suggest that Associations are perhaps not the best starting point for what you want to do, if only because they are a quite recent addition to Mathematica. And you may want to consider working with a simple list of rules first. However, here's my interpretation of what you are trying to do:

First I make some data like what I think you are trying to use:

list = StringSplit[
  "This is an interesting string with words that do not repeat"]

giving

{"This", "is", "an", "interesting", "string", "with", "words", \
"that", "do", "not", "repeat"}

Now build an association from it and name it:

anAssociation = <| Table[list[[i]] -> (0.0 + 0.005*i), {i, 1, Length[list]}]|>

This gives:

<|"This" -> 0.005, "is" -> 0.01, "an" -> 0.015, "interesting" -> 0.02,
  "string" -> 0.025, "with" -> 0.03, "words" -> 0.035, "that" -> 0.04,
  "do" -> 0.045, "not" -> 0.05, "repeat" -> 0.055|>

Here are the keys from this Association:

Keys[anAssociation]

which gives

{"This", "is", "an", "interesting", "string", "with", "words", \
"that", "do", "not", "repeat"}

And let's extract the numerical values associated with the strings

Table[anAssociation[[list[[i]]]], {i, Length[list]}]

which gives:

{0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055}

or you could do this with a pure function

anAssociation[[#]] & /@ Keys[anAssociation]

which gives the same result.

But a perfectly workable approach uses replacement rules directly.

Define a set of rules for replacing strings by numerical values

stringRules =  Table[list[[i]] -> (0.0 + 0.005*i), {i, 1, Length[list]}]

giving

{"This" -> 0.005, "is" -> 0.01, "an" -> 0.015, "interesting" -> 0.02, 
 "string" -> 0.025, "with" -> 0.03, "words" -> 0.035, "that" -> 0.04, 
 "do" -> 0.045, "not" -> 0.05, "repeat" -> 0.055}

Now pick any of the strings and use the rule to get the first value in the rule list corresponding to that string. For example

 "words" /. stringRules

Gives

 0.035

A good place to start learning about Mathematica programming is Paul Wellin's book

http://www.amazon.com/Programming-Mathematica-Introduction-Paul-Wellin/dp/1107009464/

It's a pretty up-to-date treatment--through version 9.