I can't tell you how many parents have asked me questions like this.... "my 3 year old isn't talking very much.... do you think she needs speech therapy?" or " my son can't pronounce his sounds... does he need speech therapy?"
After 18 years in this field I can confidently say that all children do not acquire speech and language in exactly the same way or at the same pace. But years of research have demonstrated that, although there is a very wide range of "typical" development, we do have some very clear guidelines to help parents determine whether they should seek the expertise of a qualified Speech Language Pathologist. That is the very reason The American Speech Language Hearing Association began the Identify The Signs Campaign to help raise awareness of the early warning signs of communication disorders.
Does your child have any warning signs of a communication disorder?