The hammer rang once. A spark jumped off the anvil and did not go out. It waited. They followed.

The February issue of the Green Gazette had a survey on the front page, and Tara was proud of it. Surveys were hard. People did not fill them in, or they filled them in as a joke, or they wrote none of your business across the top.

Hattie had done it anyway. Hattie was in Year 11 and had a Saturday job at the garden centre, and she had wanted to know what everyone else was paid. She had put a short form in the Gazette box and on the noticeboard outside the library. One question: How much did you earn from your Saturday job last week? Twenty-five people had answered. She had added up every reply on her phone, twice, and then a third time on paper.

The headline ran across the top in thick black letters:

SATURDAY JOBS PAY £48 A WEEK ON AVERAGE, GAZETTE SURVEY FINDS

Under it was a photograph of a till, and a paragraph that said the average student with a Saturday job earned forty-eight pounds a week.

By Tuesday it was the most talked-about thing the Gazette had printed all year. People argued about it at lunch. A Year 8 boy asked Tara whether it was true that you could get forty-eight pounds for one day. A girl in Year 12 said she was going to ask for more money.

On Saturday there were two letters in the Gazette box.

The first was typed, on paper with a heading: Fenwick's Books, the Green. Tara knew Mr Fenwick. He had sold her Danya's Christmas present in December.

Two of my Saturday staff have asked me for a rise, the letter said. They showed me your front page. I pay them thirty-two pounds for a four-hour shift. That is more than the law asks me to pay someone their age. I am not a rich man and it is not a rich shop, and I would like to know where forty-eight pounds came from.

The second letter was handwritten, on a page torn out of an exercise book. It was from Bea in Year 9.

I wash up at the bakery on Saturdays, it said. I get fifteen pounds. I thought it was fine until I read your paper. Now I think I'm being cheated. I asked for more and they said no and now it's awkward. Is forty-eight pounds really normal?

Tara pinned both letters to the board above the back table at the Whetstone café. She looked at them for a long time.

She had been proud on Tuesday. Now she was uneasy, and she did not know why yet.

"I was going to say the average is right," Tara said.

She had brought the letters to the back table. Danya was there, eating a cheese scone and doing his science homework at the same time. Across from him sat Sofia, who wrote the Gazette's sports pages and kept every result of every school team in a notebook with a green cover. Sofia did not trust any number she had not seen written down beside all the others.

"I was going to say it like this: Hattie added up all twenty-five replies and divided by twenty-five," Tara said. "That's what an average is. She did it three times. The sum is right. I can write back to Mr Fenwick and Bea and say so."

She already had the sentence half written in her head. Thank you for your letter. Our figure is the correct average of the replies we received.

It felt good. It felt like the end of the conversation.

Sofia read both letters slowly, and then she put them face down.

"The average is only half the story," Sofia said. "It can be exactly right and still tell you almost nothing about a normal Saturday. Before we answer anybody, I want to see all twenty-five."

"Why? Hattie's already added them up."

"Write all twelve down first," Sofia said. "I always say that to the football team when they tell me they're a three-goal side because they scored three goals one week. Here it's twenty-five, not twelve. But the idea's the same. I want every reply in a row, in order, so we can see it."

"Says who that it's half the story?" said Danya, through scone.

"Every team has a spread, and Mr Fenwick shows ours without knowing it," said Sofia. "He pays thirty-two pounds. Bea gets fifteen. Neither of them is anywhere near forty-eight. I'd like to know who is."

Tara opened her mouth. Then she shut it again.

"How do we know anybody is?" Danya asked.

Nobody knew. That was the problem.

Deed came in at eleven, with a bag of oranges and a library book about the history of drains. Deed read council minutes for fun. She kept every planning application on her phone, sorted into folders. She had once found a mistake in the town budget on page two hundred and nine, and she had never stopped being pleased about it.

Tara showed her the front page and the two letters.

"Where's the sheet?" Deed asked.

"What sheet?"

"Go to the original document," said Deed. "The story says forty-eight. That's Hattie's summary. The thing she summarised is twenty-five replies on twenty-five bits of paper. Hattie will have them somewhere. A summary of a summary drifts, and this is only a summary of one step, but I still want to read it where it was first written down."

Tara texted Hattie. Hattie replied in two minutes, with a photograph of a single sheet of lined paper. On it, in Hattie's neat handwriting, were twenty-five numbers. Next to each was the job, and nothing else. No names.

Deed turned the phone round so everyone could see.

The numbers were in the order the forms had come in. Twenty here, fifteen there. Twenty-four. Thirty-two. Twelve. They were all close together, mostly between ten and fifty.

Then there were two that were not.

£350 — selling trainers online.

£300 — DJ at a wedding.

"Show me the source, then," said Danya, leaning in. "What were the others?"

Deed added them up on her phone while the others watched. It came to twelve hundred pounds.

"Read it where it was first written down: twelve hundred pounds, shared out between twenty-five people, is forty-eight pounds each," said Deed. "Hattie's sum is right. The headline is the true mean of her replies. I'd have got the same."

"So it's accurate," said Tara.

"It's accurate," said Deed. "Page one, line by line. Here." She tapped the two big numbers. "And there's the reason it looks like that."

Sofia had already taken out her green notebook. She turned to a clean page and wrote the twenty-five numbers down, smallest first, in a single long column. It took her four minutes. Nobody talked while she did it.

Ten. Twelve. Twelve. Fifteen. Fifteen. Sixteen. Eighteen, eighteen, eighteen. Twenty, twenty, twenty, twenty. Then twenty-four, twenty-five, twenty-six, twenty-eight, thirty, thirty-two, thirty-eight, forty, forty-six, forty-seven.

Then a gap.

Then three hundred, and three hundred and fifty, sitting at the bottom of the column like two boulders at the end of a garden path.

"Look at the whole season, not one game," said Sofia. "Now count down to the middle. Twenty-five replies, so the middle one is the thirteenth. Twelve above it, twelve below it."

Danya counted with his finger. "Thirteen," he said. "It's twenty. Twenty pounds."

"Look at the whole season: half of them earned twenty pounds or less," said Sofia, "and half earned twenty or more. That's what a normal Saturday looked like, in Hattie's survey. Twenty pounds."

Tara stared at the column.

"Write them down and count. How many earned less than forty-eight?" Sofia asked.

Danya counted again, slower this time. He went all the way down to forty-seven and stopped.

"Twenty-three," he said. "Twenty-three out of twenty-five. Only two people earned more than the average."

"Who checked that before it went on the front page?" said Danya. "That's mad. The average is more than nearly everyone got."

"It's not mad," said Sofia. "It happens whenever a couple of numbers are much bigger than all the rest. Every team has a spread. Most weeks you score one or two. Then once a season you win eight-nil, and if you only look at the average, you think you're a three-goal side."

Tara thought about Bea, washing up for fifteen pounds and reading that forty-eight was normal.

The average was a true number. Hardly anybody earned it.

Widen arrived with a takeaway hot chocolate and a calculator that he did not need. Widen wrote the Gazette's money pages. He kept a small notebook of what things cost, from a bus ticket to a bridge, and he could not hear a number without wanting to put another number next to it.

He read the front page, the letters and Sofia's column, one after another.

"Compared with what, though?" said Widen. "Forty-eight pounds compared with what? Let's widen the view. What happens to the average if those two aren't there?"

"We can't take them out," Tara said quickly. "That would be cheating. Callum really did earn three hundred and fifty pounds. I know it's Callum, everybody knows he sells trainers."

"One number on its own tells you almost nothing, and I'm not taking them out of the paper," said Widen. "I'm taking them out of the sum for one minute, to see how much they're doing."

He did it on the calculator anyway. Twelve hundred, take away three hundred and fifty, take away three hundred. Five hundred and fifty pounds. Shared between the other twenty-three.

"Compared with forty-eight, it's about twenty-four pounds each," said Widen.

He wrote it in his notebook. Then he wrote 48 next to it and drew a line between them.

"Is that a lot, or does it just sound like a lot?" Widen asked. "Two people, out of twenty-five, doubled the average on their own. Forty-eight is about twice twenty-four."

Tara looked from the column to the notebook and back again.

"Can I say one thing?" Tara asked. "So the front page was wrong?"

"Not wrong," said Sofia. "True and half told. The mean was right. It just wasn't the number Bea needed. She needed the middle one."

"And Mr Fenwick," said Widen. "Thirty-two pounds for four hours is above the middle. He's paying more than most of the people who answered. Our front page made him look mean, and he isn't."

Attest came last, carrying the Gazette's red pen. Attest subbed every story before it went to print and drew a red circle round any number that did not have a name next to it. The February front page had come back with one circle on it, round the words on average. Nobody had noticed, because the circle wasn't round a number.

"Where did that number come from? I wondered whether someone would ask," said Attest.

"You could have said," said Tara.

"I circled it," said Attest. "Where did that number come from? That's what a circle asks. I knew it was a mean. I didn't know what the middle was. Nobody did, until Sofia wrote the column."

"Let me listen first," Tara said, before anyone could start explaining. She had learned that in the autumn, from the photo of the flooded underpass, and again in January, from the energy-drinks box. She took out a pad and wrote three headings across the top: what we printed, what the sheet says, what is missing.

Under the first she wrote £48 on average. Under the second she wrote 25 replies, total £1,200, middle £20, 23 below £48. The third column stayed empty for a while. Then she wrote the typical one.

"Hm. So what does a clarification like this have to carry?" Tara asked.

"Every claim names its source," said Attest. "This one's our own survey, so it says so. It has to carry both numbers: the average and the middle. It has to say how many replied, twenty-five. And it should say that these were the people who chose to fill in the form. That's not the same as everybody with a Saturday job."

"Do we take Callum out? Or the DJ?"

"No," said Attest. "Nobody's reply gets taken out. They're real. Put a name next to it, and say what kind of number each one is. The mean, and the middle. That's all."

"Hm. That's a lot for one box," said Tara.

"It's two sentences," said Attest. "Maybe three."

Tara looked at Bea's letter again, with its torn edge. Is forty-eight pounds really normal?

"I think we missed someone," Tara said slowly. "Callum. If we print 'only two people earned more than forty-eight', everyone will know one of them is him. It'll look like we're saying he doesn't count."

Nobody answered at once.

"A correction names its source too," said Attest. "Who you name is your call. That's your bit."

Mrs Hallam, who advised the Gazette and signed off every issue, came in at noon. Hattie came with her, looking as if she had not slept. Mr Fenwick came ten minutes later, in his coat, with his reading glasses on a cord. Bea did not come. She had sent a message through Danya to say she was too embarrassed.

Hattie spoke first.

"I did the sum right," she said. "I did it three times. That's the average. If I'd taken out the two big ones, that would have been cooking the numbers. You'd have told me off for that, Tara. You'd have said I was hiding the people who didn't fit."

It was the strongest version of her argument, and she was right about it.

Then Callum's message came through on Hattie's phone, because Hattie had told him what was happening. He had typed it fast.

Don't make me the problem. I worked for that money. I was up till two packing parcels. It's real. If you print that the average is wrong because of me, everyone will think I lied.

Mr Fenwick spoke next. He was quiet and polite and he looked tired.

"I am not asking you to take anything back," he said. "I am asking you to understand what it did. I pay above the minimum. I've paid above the minimum for twenty years. Two very good people now think I've been underpaying them, and one of them nearly left. That's what your forty-eight pounds did in my shop."

"I didn't mean to make you look mean," said Hattie.

"I know," said Mr Fenwick. "You didn't. A number did."

Then Danya read out Bea's message, because she had asked him to.

I don't want to be in the paper. I just want to know if fifteen pounds is normal for washing up. I felt really stupid.

Nobody said anything for a while.

Mrs Hallam took the corrections box out of her bag. It was a small grey panel at the bottom of page two, with a border round it and room for a few lines. She had used it five times that year. She set it on the table in front of Tara, with the February front page beside it.

On the table in front of Tara were Hattie's sheet of twenty-five replies and Sofia's column, smallest first. There was the middle number, twenty pounds, with a circle round it. There was Widen's twenty-four pounds, with a line to the forty-eight. There was Attest's list of what the box had to carry. And there were three letters: one typed, one torn out of an exercise book, and one on Hattie's phone, typed at speed by somebody who had been up till two packing parcels.

"You're the editor," said Mrs Hallam. "What does it say?"

She handed Tara the pen.

Tara looked at the empty box.

 

 

(Write the line Tara prints in the corrections box.)

 

The spark dimmed to a warm dot and settled back on the anvil. The Green was just the Green again.

Back on the Green

That week Lan, who was seven, came home from school and said that the average height in her class was taller than her.

Danya asked her who the tallest one was. Lan said Marek, who was nearly as tall as the café door. Danya asked her to stand everybody in a line in her head, from shortest to tallest, and to tell him who was in the middle.

Lan thought about it very hard and said Priti.

Danya asked how tall Priti was. Lan said exactly the same as her.

Lan looked surprised, and then very pleased, and went to tell her grandmother she was the middle.

Afterword. The idea in this case is the difference between the mean and the median. The mean is what most people call the average: add everything up and share it out equally. The median is the middle value when everything is written in order. When a few values are much bigger than the rest, as with two unusual weeks in a pay survey, the mean is pulled far above what a typical person gets, while the median stays put. Both numbers are true; each tells you something different. Good reporting gives both, says how many people were counted and how they were chosen, and never takes a real reply out to make the numbers tidier. You can practise writing a set in order and finding its middle, and seeing how far one big value moves a mean, in InferForge, and putting a number next to another in NewsForge.