We are coding a statistics calculator.

In this case we have input of some numbers and the calculator will generate some output.

A quick object diagram tells us about the main object and its components (ivars).

We'll call our object type (class) "Stats" and it has one component "nums".

Where Stats abbreviates StatisticalCalculator and "nums" abbreviates "numbers".

We simplify the diagram here to a simple textual diagram.

Simple is good. Your choice.

Our object diagram (whichever we choose) is our "blueprint" as we begin coding.

We should keep it handy to reference.