I would think that the conclusion about hysteria has to discuss how Miller's work deals with it and the implications from it. The form of this might be up to the reader. I think that a necessary component of this conclusion would be how Miller views the issue of hysteria. Perhaps, this explanation would talk about how individuals, when they acquiesce to it, sacrifice their moral courage or their voice. Another element of this conclusion might be its opposite: A great deal of moral strength is needed to stand up to hysteria and fight the forces of those who wish to silence discussion in the consolidation of their own power. This could find relevance in Miller's own experience with McCarthhyism, where the negative impacts of hysteria were on full stage for all to see.
If you are writing a standard essay with a conclusion which restates your thesis, make sure that you include that thesis first. Following that sentence, try to broaden out your conclusion to discuss hysteria in general. You might make a comparison between the Salem witch hunt and other witch hunts such as McCarthyism, the Inquisition, or even the Kansas Sex Ring scandal (in which children were coaxed to accuse religious leaders of improper sexual contact--all accusations were later discovered to be false). You might also discuss how hysteria can cause people to set aside not only logic but also religious beliefs, long-established personal relationships, and even family ties.
In general, a conclusion should present a truth that can apply not just to the literary work (such as The Crucible) but to the human condition.