If Todd Cabell, senior manager of e-commerce at Crutchfield Corp., had any doubt about the wisdom of adding PayPal Mobile Express Checkout to the electronics retailer’s mobile commerce site, it vanished following testing that showed the payment option increased the mobile conversion rate by 33.7% in an April through May  A/B test where some consumers were given the PayPal option and some were not.

He attributes that welcomed boost to the payment method’s simplicity. A mobile shopper using PayPal Mobile Express Checkout only need enter his PayPal user name and password to authorize transactions. PayPal stores its account holders’ PayPal and other payment card data, and the billing and shipping addresses. That is much simpler than entering a 16-digit card number, expiration date and verification code via a mobile phone, and possibly multiple addresses, Cabell says. “Clearly, a lot of our customers want to use it,” he adds.

Though Cabell declined to reveal total m-commerce sales or say what percent of Crutchfield’s sales come from its m-commerce site, he says they are growing. “It will continue to grow in the coming years,” he says.

Integrating PayPal Mobile Express Checkout into the m-commerce site took two and a half weeks, in a process made simpler because Crutchfield completed PayPal integration into its e-commerce site in November, Cabell says. Crutchfield had not accepted PayPal transactions on either its e-commerce or mobile commerce sites prior to then.

“During that implementation process we had been thinking about how useful PayPal would be for people shopping on our mobile site,” he says. Crutchfield worked with technology provider Usablenet Inc. to incorporate PayPal Mobile Express Checkout. Usablenet and PayPal announced in January the two companies were working together to add PayPal’s mobile checkout feature to Usablenet’s products.

PayPal launched Mobile Express Checkout in October 2010.