Is a striped black and yellow spider deadly?

I don't know where you are. There is no poisonous yellow and black spider in North America. The only poisonous Spiders in North America are the black widow and brown recluse. All others are beneficial because of the insects they eat.

We need to know where you are, where you saw the spider, size of spider, what the web (if any) looks like, was spider "hairy" or shiny?

It sounds like a common orb weaver, aka common garden spider or Black and Yellow Garden spider, Argiope aurantia, which are way cool. They build a huge web every evening to catch mosquitoes and other flying insects. The next morning they often actually eat the web and go off to hide till evening. Watching them spin the web is really something.

Go to google Images and look up Argiope aurantia, see if it the one you saw.

Do a regular google search for Identify Spider and you'll see sites where you can see many spiders including poisonous ones and webs.

Below are some links to Yellow Orb Weavers, check out the rest of site too.