website design - Should radio buttons be pre-selected?

I am working on a re-design for a eCommerce site and they have a section where they offer a free gift card if the user makes a purchase over $1000. The idea of the gift card is to get users to purchase more on the site and since the products are generally expensive (its a jewelry site) chances are they will spend the gift card plus some more money on the site.

So the question I have is should the radio button group which asks user if they want a free gift card be pre-selected ?

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There are two aspects to it which I am trying to consider and I would appreciate it if answers consider those a parameters

1. The user experience if the radio button is pre-selected as yes and the user is wondering when did he sign up for a gift card even though its free


2. The aspect of conversion from a e-commerce perspective

Answer

First of all: why do you ask at all? Why not simply always send the gift card with the order? Who would object to getting more value than what they ordered? If you don't ask, you don't have your problem to begin with. Generally, asking fewer questions from the user results in higher conversion, so from that perspective, removing the whole question would be an obvious step to take. As long as they don't cash the gift cards, there is no cost incurred for the shop, and if they do and spend more money besides, you'll have reached your goal with including them in the first place.

But if you insist you need to ask: radio button groups should always have exactly one selected item. So, that would mean that you should indeed select one of the items. What is the meaning of a group of radio buttons without a selected item? However, for a yes-or-no question, I don't think a radio button is the right control to use. Instead, use a check box.