To solve this problem, we can use Bayes' theorem and organize the information given into probabilities:
- Let  T  be the event that a patient receives the treatment.
- Let  I  be the event that a patient experiences significant improvement.
From the problem statement, we have:
-  P(I|T) = 0.30  
-  P(I|T^c) = 0.20  
-  P(T|I) = 0.60  
We need to find  P(T|I) , the probability that a patient received treatment given that they improved. 
Using Bayes' theorem, we can rewrite  P(T|I)  as:
 P(T|I) = \frac{P(I|T)P(T)}{P(I)} 
Let's find  P(I)  using the law of total probability:
 P(I) = P(I|T)P(T) + P(I|T^c)P(T^c) 
Assume the proportion of patients who received treatment is  p , then:
 P(T) = p \quad \text{and} \quad P(T^c) = 1 - p 
Substitute these into the equation:
 P(I) = 0.30p + 0.20(1 - p) 
Solve for  p  using the equation  0.60 = \frac{0.30p}{0.10p + 0.20} . The solution for  p  is 0.5, meaning that 50% of the patients received treatment.
Now, find  P(I) :
 P(I) = 0.10p + 0.20 = 0.10(0.5) + 0.20 = 0.25 
Finally, the probability that a patient who received the treatment will experience significant improvement is  P(I|T) = 0.30 .
Therefore, the probability that a patient who received the treatment will experience significant improvement is **30%**. 
\boxed{P(I|T) = 0.30}