The lesson
The weather report before the fire
I normally serve about 150 bowls a day. The weather report says rain at six this evening. For most people, that is a hassle. For me, it is a number. Friday night is my biggest sitting, and in heavy rain, part of the after-work crowd goes straight home instead. Cook too little, and the pot is empty by 8. Cook too much, and I am feeding the rubbish bin at closing. How much I throw away tonight is a number between the two. And I have to tell the butcher my lamb order by 10 this morning.
Thousands of Fridays, one feel
This is where experience counts. I have served through thousands of Fridays, and I have a feel for the answer. The rain. The day of the week. Whether the office towers down the road are on holiday. I cannot write the formula down for you. But ask me for a rainy Friday, evening crowd, full offices, and I will give you a number that is close. That is regression: predicting a number from the factors that move it. A machine fed the same history does the same job, and it can hold more Fridays than any publican could live through. So classification sorts things into groups. Regression puts a number on the table.
The number behind the bus app
You met this model today without noticing. The bus app that says 4 minutes to arrival is regression. The supermarket deciding how many sacks of potatoes to stock this week is regression. Past patterns in. One number out. And no, 4D and TOTO are not regression.
Your Friday to call
Let me give you a Friday.
There is rain at six. The offices down the road are full. How many bowls will I sell tonight? I give you three seconds.
Pause here for three seconds.
Show the answer
… 85.
If you landed between 70 and 100, you did exactly what the model does. The rain pulled you down. The offices pulled you up. You committed to a number. The model has seen more Fridays than you.