Consumers on iPads spend significantly more time and money on e-commerce sites than consumers on smartphones and other tablets, suggests a study of 75 retail sites by personalization vendor RichRelevance.

In March 2012, 68% of mobile shoppers accessing retail web sites used iPads, RichRelevance finds. The iPad accounts for 90% of all mobile revenue and 4% of total web revenue. Conversion rates are strongest with the iPad: 1.5% for the iPad versus 0.57% for other mobile devices. And the average pages per session figure was highest for the iPad compared with all other mobile devices: 5.7 pages for iPads, 3.6 pages for iPhone and 4.1 pages for other mobile devices.

The study likely would return some higher results for smartphones if m-commerce sites were included, mobile experts say. Consumers must pinch and zoom and swipe their way around an e-commerce site on a smartphone versus having an m-commerce site that is tailored to the size of a smartphone screen. RichRelevance said almost all of the sites in the study were e-commerce sites, which an iPad would access, not m-commerce sites, which a smartphone would access.

Consumers on iPads spent dramatically more in March, though on fewer items, than other mobile shoppers. When compared to online shoppers, iPad users spent approximately the same amount on an average order, but bought much more expensive products. IPad shoppers averaged $52.66 per item versus $21.86 per item for desktop users and $23.80 for other mobile users, the study finds. Further, the iPad had the highest average order value of any mobile device on an e-commerce site: $158 for iPad, $105 for other mobile devices, and $104 for the iPhone and iPod Touch.

The average order value for iPad shopping is creeping ahead of the same for desktop computer shopping: $158 for iPad shoppers versus $153 for desktop consumers in March. While they spend more per average order, iPad shoppers had on average fewer items per order of any mobile device: 2.98 for the iPad, 4.22 for the iPhone and iPod Touch, and 4.41 for all other mobile devices.

It seems iPad shoppers are weekenders. The iPad’s share of total shopping sessions, viewing but not necessarily buying, hits 7% on weekends versus 5% on weekdays, RichRelevance finds. By comparison, traffic from all other mobile devices is stable on weekdays and weekends, accounting for about 1.3% of all sessions. On average in March, about 6% of all orders originated on mobile devices (the iPad included) on weekends versus 4% on weekdays.

The RichRelevance Shopping Insights study is based on more than 4.4 billion shopping sessions on 75 U.S. retail web sites, all clients of the vendor. Retailers range from mass merchants to small, specialty retailers. Retailers studied include 10 of the 25 largest retailers on the web, RichRelevance says.