# Setting Reference & Tolerance Values

When you assign a test list to a unit each of the tests from that list are assigned a record of the reference value and tolerance/action levels on that unit. Reference values and tolerance/action levels are unit specific so you must set these values for every unit a test is assigned to. Initially the reference value and tolerance/action levels are set to null so you will need to update them if you want to subject your tests to pass/fail criteria when performing a test list.

To set the reference and tolerance values click on the Set References and Tolerances link from the main admin page. From here you will see a list of all the test/unit pairs for any test list which has been assigned to a unit. To set the reference value for a given test on a unit you can either browse through the list or use the search box at the top of the page to find the test you are looking for. Note, you may also use the filters at the side of the page to narrow your search. The image below shows a search for a test which has been assigned to two units.

Once you have located the test/unit pair you want to set the reference for, click on its name. From here you will see information about the current reference value and tolerance/action levels including when these values were last changed and who changed them.

## Numerical References & Tolerances

If the test you are setting reference values for is numerical (e.g. simple numerical or composite test types) you can choose a tolerance/action level from the Tolerances: drop down and set the reference value in the text box below that.

The tolerance/action levels of a test act as a window around the reference value. For example if a certain test on a unit has reference value of 50 and a tolerance/action level of +/- 2%/3% (i.e. lower action = -3%, lower tolerance = -2 %, upper tolerance = 2%, upper action = 3%) then values between 49 and 51 will be considered within tolerance, values between 48.5 & 49 or 51 & 51.5 will be considered at tolerance and values less than 48.5 or greater than 51.5 will be considered failing.

## Boolean References

For boolean tests there is no tolerance/action levels. You just choose whether the reference value is Yes or No and when performing a test list, if the users answer matches the reference value the test will be considered passing. If the answer doesn't match the reference value it will be considered a failing result.

## Multiple Choice References

Multiple choice tests have no reference value. For information about multiple choice tolerances, please see the tolerances page.

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