**Why do I need to change values?**

There are two reasons you would want to change values:

- To be able to test situations that are not yet tested
- To make it easier to tell if values in some of the other cells are right or wrong

**How do I choose values to be able to test new situations that are not yet
tested?**

Look at some formulas for ideas. For example, if there is a comparison in a formula (using >, <, =) you may want to try one situation where one value is greater than the other, one in which it is less than the other, and one where they are equal.

**How do I choose values to make it easier to tell if values in some of the
other cells are right or wrong?**

Sometimes it’s hard to tell if a cell’s value is right or wrong.
Choosing easy values that it relies on sometimes makes the decision easier.
Try values like 0, 1, or multiples of 10. Values like these can make it easy
to notice if all the formulas that use that value are doing the right arithmetic.
For example, if cells labeled quiz1 and quiz2 were given a value of 10 each,
and the quiz_average is 9, it is clearly wrong!