Mobile performance is not about fun and games, but if you’re a toy retailer it can a reason for celebration. That is, if you are doing well.

ToysRUs.com moved up five spots on the AppDynamics/Mobile Strategies 360 3G Index to No. 16 from No. 21 the previous week.

“The most significant mover was ToysRUs.com, which jumped up five positions mostly on the basis of an almost two second improvement in visually complete time,” says Peter Kacandes, senior product marketing manager, mobile, web and synthetics, for AppDynamics. Visually complete time measures how long it takes until the web browser has completed drawing the visual elements of a mobile home page.

ToysRUs.com’s visually complete time on 3G for the week ending April 24 was 20.6 seconds, an improvement from 22.5 seconds the previous week, but still four seconds above the index average of 16.6 seconds.

On 4G, ToysRUs.com moved up one spot to No. 17 from No. 18. Toys “R” Us Inc. declined to comment.

Also on the 3G index, Clevelandclinic.org fell three spots to No. 19 from No. 16 with a 0.4 second increase in start render time, or the time it takes for the web browser to start drawing the visual elements of the mobile site home page, Kacandes says.

For the week ending April 24, Cleveland Clinic’s mobile site start render time was 6.8 seconds, compared to 6.4 seconds the previous week. This is right around the 3G index average of 6.7 seconds. Cleveland Clinic did not respond to a request for comment.

Many of the mobile sites at the top of the 3G index held their positions or merely swapped places because of minor variations in their numbers, Kacandes says. For example, Etsy.com kept its No. 1 spot, as did No. 2 Gilt.com, but TheCheeseCakeFactory.com jumped a spot to No. 3, bumping Costco.com to No. 4.

The exclusive AppDynamics/Mobile Strategies 360 Index tracks key mobile site metrics across a range of sites to calculate a weekly average Speed Score on both 3G and 4G mobile carrier networks. The index represents a snapshot of mobile site performance across industries, including retailers such as HSN.com, insurance companies such as NorthwesternMutual.com and restaurants such as McDonalds.com.

AppDynamics each week measures performance metrics of both 3G and 4G networks for each of the 30 sites in the index to determine each site’s Speed Score.

They include:

First render: The time, (in seconds) it takes until the web browser starts drawing the visual elements of a home page.

Visually complete: The time (in seconds) it takes until the web browser has completed drawing the visual elements of a home page.

Number of elements loaded: The number of resources loaded by a home page.

Complete load: The size of the home page when all data is loaded (in megabytes).

Using these metrics, the index calculates the Speed Score. The Speed Score is a ratio that rewards businesses for displaying more visual content on the mobile home page earlier rather than later. The earlier a mobile site home page looks complete to a consumer, the better the mobile experience for the visitor, even if a few remaining elements are displayed later. A site with a higher ratio of content displayed earlier will have a better Speed Score than a site with the same visually complete time but a longer first render time.

For example, site A may have a visually complete home page load time of three seconds, loading 90% of its content in the first second and the remaining 10% in seconds two and three. Site B may have the same three-second visually complete time, but present zero content in the first two seconds and 100% in the third second. The sites have identical visually complete times, but Site A will be perceived as much faster, and will earn a better Speed Score as a result.

The index is accompanied by a chart on MobileStrategies360.com that is refreshed weekly to illustrate how each mobile site performs as well as index averages. Click here to access the performance chart for the week ending April 24.