eValid™ -- Automated Web Quality Solution Browser-Based, Client-Side, Functional Testing & Validation, Load & Performance Tuning, Page Timing, Website Analysis, and Rich Internet Application Monitoring.

Summary
The Apdex Application Performance Index is a performance metric for web pages that has been created by the Apdex organization, an industry-sponsored technology promotion group. The Apdex Index seeks to provide an unambiguous way to compare the performance of websites, and to measure the relative performance of pages within a website.

The Apdex Index is based entirely on relative page loading times, and on a pre-defined threshold time value T (recommended T valud is 4.0 secs) below which a user is presumed "satisfied" with the performance. Pages that load slower than four times T (16 seconds, for example) are called "tolerating", and anything slower is called "frustrated".

The index formula is

Apdex-Index(T) = ( #satisfied + ( #tolerating / 2 )/ ( #total ) )

A typical application of the Apdex Index is to rank order Business IT Alignment when different parts of a website (i.e. subwebsite) are aiming at difference performance levels.

Step By Step Instructions
Here are the steps to follow to have eValid calculate the values you need to compute the Apdex Index for you.

1. Navigate the eValid browser to starting page of the website.

2. Choose the Settings protocols to include *html and *htm protocols only. This assure you will only be visiting *html and *html pages, i.e. complete pages, and not *gif's or *jpg's, etc.

3. Choose the Setting for page speed to be "pages slower than 1 msec." This assures that all of the pages and their times will show up in the Slow Pages report.

4. Start the site analysis process and wait for the run to complete.

5. Using the Speed report calculate the three values (look at the download times):
   1. Choose "T" (default here T = 4.0 sec).
   2. Count how many tests are faster than T (from 0 to T sec.)
   3. Count how many tests are between T and 4 * T
   4. Count how many tests are slower than 4 * T (the rest of the tests).
   5. Note how many tests there were in all (this number is at the top of the report).

6. Calulate the Apdex Index value using the formula above.

Interpreting the Scores
According the the Apdex website, you should interpret the scores following this table:

Range	Score
1.00 - 0.94	Excellent
0.94 - 0.85	Good
0.85 - 0.70	Fair
0.70 - 0.50	Poor
Below 0.50	Unacceptable