What criteria should be used for the priority and frequency of change in an XML sitemap?

On what criteria can we set the priority and change the frequency in the sitemap.

Example if the website is a coupon / service website.

  • The welcome page must be a priority 1 updated daily
  • Category pages must be prioritized 1 Updated daily
  • Coupon pages must have priority 0.5 Updated weekly

Are the above settings correct?