Assuming that you're using anonymous links which are being distributed, what you can possibly do is use two embedded fields which are Email send date and Status whether survey is completed by user or not.

You can then go into custom metrics and divide count of status and email send date in order to get response rate for that particular date.

If you have already gathered responses, then you can update the responses with the send date and status fields such to calculate the response rate.

Thank you for your response.
Actually, I am using personalized links. So, I actually know the sample size.
Can I still implement your suggestion?

Yes you can implement the above proposed solution

I do not have CX Dashboards under my license. Is that a problem?

Without CX dashboard it will not be possible to calculate the score unfortunately :-(

I was afraid of that.
Thanks for your help.