New docker installtion does not find the docker daemon on Ubuntu

I am running Ubuntu 18.04.2 desktop and I installed the community edition of docker following the instructions in https://docs.docker.com/install/linux/docker-ce/ubuntu/. I followed the scenario to install docker from the docker repository. When I try to run hello-world the following situation arises:

jgossage@JFG-Ubuntu-18:~$ ps -ef | grep docker
jgossage  4619  4604  0 09:35 pts/0    00:00:00 grep --color=auto docker
jgossage@JFG-Ubuntu-18:~$ getent group docker
docker:x:999:jgossage
jgossage@JFG-Ubuntu-18:~$ ls -Al /run/docker*
srw-rw---- 1 root docker 0 Mar 20 09:23 /run/docker.sock
jgossage@JFG-Ubuntu-18:~$ docker run hello-world
docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
See 'docker run --help'.
jgossage@JFG-Ubuntu-18:~$ sudo docker run hello-world
[sudo] password for jgossage: 
docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
See 'docker run --help'.
jgossage@JFG-Ubuntu-18:~$ docker run hello-world:nanoserver
docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.
See 'docker run --help'.
jgossage@JFG-Ubuntu-18:~$ 

As you can see, the docker daemon appears to be running and the socket exists. Are there any suggestions on how to diagnose this situation? I am not a hard-core Linux person, simply a user.