Lea writes: "Dr. Cruz, a volcanologist at the national institute, reports that the ash fall has stopped." What form of support is Lea using?

Ramon writes: "I rode this jeepney once and it was crowded, so every jeepney on this route is crowded." What form of support is Ramon using?

A team writes: "We counted the birds in the mangrove at dawn every Sunday for one year and recorded each count." What form of support is this?

An essay states: "A part of a thing is smaller than the whole thing it belongs to," and offers no proof. What form of support is this?

A leaflet says: "The city health office advises boiling drinking water for one minute after a flood." What form of support does the leaflet use?

Ana writes: "My grandmother drank this tea and her cough went away, so this tea cures coughs." What form of support is Ana using?

A report says: "We tested 400 water samples from twenty wells and listed every result in a table." What form of support is this?

A writer states: "Every square has four sides," and moves on without giving any evidence. What form of support is this?

Jun writes: "The engineer who inspected the bridge last month says two of its cables need replacing." What form of support is Jun using?

A blog says: "I once waited two hours at one clinic, so public clinics waste a person's whole day." What form of support is the blog using?

A study says: "Weather stations recorded rainfall every hour across the province for three months." What form of support is this?

A speaker begins: "No person can be in two places at the same moment," and gives no proof at all. What form of support is this?

A textbook supports its account of how children learn new words by citing a professor of linguistics. What form of support is the textbook using?

Kim writes: "My bag was taken on that bus, so every driver on that line steals from riders." What form of support is Kim using?

A dentist states that fluoride toothpaste lowers the number of cavities, and a writer cites her for it. Is this a sound appeal to authority?

A famous chemist appears in an advertisement recommending one brand of running shoes. Should a reader treat her word as expert support?

A heart doctor says the mountain province is the most beautiful place in the country. Can her expertise settle this question?

A film star says in an advertisement that a vitamin drink prevents colds. Is this a sound appeal to authority?

A civil engineer states the load limit of a bridge she designed and inspected. Is citing her a sound appeal to authority?

A retired basketball coach explains on television why the ocean is growing warmer. How should a careful reader treat his explanation?

An economist says the government ought to spend more on parks than on roads. Can her expertise settle this?

A historian who has read a town's original records states the year the town was founded. Is citing her a sound appeal to authority?

An advertisement says: "Nine of ten shoppers choose this brand." Does this sentence appeal to an authority?

A software engineer writes a long post claiming that a certain diet cures diabetes. What is the main problem with the appeal?

A biologist says the school anthem is a finer song than the town's anthem. Can her expertise settle the point?

An agronomist reports which rice variety produced the most grain in her field trials. Why is citing her a legitimate appeal to authority?

A chef with a popular restaurant explains which language is hardest for children to learn. How should a reader treat his explanation?

A leaflet says: "Experts say the new road is safe." What most weakens this appeal to authority?

Four writers support the same claim about the soil in one neighborhood. Which sentence makes the strongest appeal to authority?

A review of a phone released this year quotes a battery manual printed in 1998. What is wrong with the appeal?

Mia says: "The lift in this building was stuck last Tuesday, because I was trapped inside it for an hour." Is her story good evidence?

Leo says: "One shop overcharged me on Sunday, so every shop in this market overcharges." What is wrong with his support?

A poster says: "Doctors recommend this soap." Which change would make the appeal checkable?

A writer quotes a chemist's judgment that a cleaning liquid is harmful, then lists the laboratory tests the chemist ran. What form of support do the tests add?

Two writers back the same claim about a river. Which support is empirical rather than an appeal to authority?

Two qualified climate scientists publish different figures for the same measurement. What should a careful writer do?

A student writes: "Our teacher says the essay is due on Friday." Is this a fair use of authority?

Argument from authority is always weak support, whatever the expert's field.

An expert's word can support a claim inside her own field, but it cannot settle a question of personal taste.

A single personal story is suitable support for a claim about one event the speaker saw.