So you are finally going to do it.

You just told the sales clerk you are ready to buy that 50-inch plasma television you’ve been wanting. You can’t wait for it to be delivered and set up for your Super Bowl party.

Next question from the clerk: “Can we interest you in our extended warranty? It’s only a few dollars more and you’ll have a couple of extra years of protection.”

The clerk has you at a weak moment during the transaction.

“These tend to get offered at times of high emotion,” Kansas University associate business professor Dennis Rosen said.

There are a lot of factors to consider about warranties, he said. You should understand the details of the warranty that comes with the product before deciding whether to purchase an extended one. Ask the clerk if you can still buy the extension after thinking about it for a few days. Then you can conduct your own investigation, such as calling repair shops or searching for information on the Internet about repair problems or longevity of a product brand, Rosen said. You could do that research before buying the product, too, he noted.

“With electronic devices, the way technology is improving and prices are going down, in three or four years you might not care about that product anymore,” Rosen said.

You also might try negotiating with the store over an extended warranty. Maybe you can get them to throw it in for free or at a reduced price. Profit margins on extended warranties are as much as 60 percent to 70 percent, Rosen said.

“With that kind of profit margin, they can afford to negotiate,” he said. “Everything is negotiable. It’s worth trying.”

Kansas and many other states have implied warranty laws. That means that a product has to perform as it is advertised.

“If you buy a high-dollar TV and it goes down in a year, is it functioning properly? An implied warranty can give you additional protection,” Rosen said.

Dealing with extended warranties is mostly a matter of keeping your eyes open and thinking about whether the warranty is likely to pay off, Rosen said.

“What people are buying is peace of mind, and for some people it’s worth the money,” he said. “We shouldn’t be buying it with the thought that the new product is going to break down immediately. If we’re buying a quality product, it shouldn’t break down.”