Multiply, then add

Now put the pieces together.

Outside, there is light rain. The weather app predicts more. Your unreliable friend is certain that it will pour.

Each input uses the same scale. 0 means no sign of rain. 1 means the strongest sign.

The input value says what each source reports. The weight says how much the neuron trusts it:

outside: 0.2 × 0.8 = 0.16

weather app: 0.8 × 0.5 = 0.4

friend: 1.0 × 0.1 = 0.1

Add the three contributions:

0.16 + 0.4 + 0.1 = 0.66

The threshold is 0.6. The total is higher, so the neuron fires. In this example, that output means: carry an umbrella.

That is the neuron's calculation: multiply each input by its weight, then add the results.