The EPEL repository usually contains quite a recent, but not always the latest version of Ansible.
To get absolutely latest, yet stable version of Ansible, add this official repository.
Create file /etc/yum.repos.d/ansible.repo:
[ansible]
name=Ansible RPM repository for Enterprise Linux 7 - $basearch
baseurl=https://releases.ansible.com/ansible/rpm/release/epel-7-$basearch/
enabled=1
gpgcheck=1
gpgkey=https://releases.ansible.com/keys/RPM-GPG-KEY-ansible-release.pub
Alternatively, you can do:
yum install https://extras.getpagespeed.com/release-latest.rpm
yum install ansible-release