Am I required to sign the settlement agreement?

No, you are not required to sign any settlement agreement at a mediation. However, the agreement will only be binding on the parties if signed.

At a mediation, the parties may reach an agreement with each other to settle the dispute. When they do this, they (or their lawyers) will draft a settlement agreement  which they will both sign.

A party is free to withdraw from the mediation without signing the settlement agreement and there is no obligation to sign the agreement. 

However, a settlement agreement becomes binding only when it has been signed.  Therefore, for mediation to lead to an enforceable final settlement, both parties must sign the agreement.