Reliable Sources
A message pops up in your class WhatsApp group: "Urgent! No classes tomorrow at any of the high schools, pass it on." Everyone forwards it within seconds. Who wrote it? Where did it come from? On the internet anyone can post whatever they want, whether it has been checked or not. Searching well is only half the job: the other half is deciding whether what you found deserves your trust. At the end of the page you'll come back to this message.
What to look for when you land on a page
Spelling mistakes are a weak signal: they can point to carelessness, but a well-written text can also lie. What matters is being able to check who is speaking and where the data comes from.
The date: publication and update
Many articles show two dates: the publication date (when it was written) and the update date (when it was reviewed). To know whether something is up to date, look at the more recent one. On topics that change fast (technology, health, prices, laws) the date is decisive. On others, like the height of a mountain or a historical fact, it hardly matters.
From this list of elements on a web page, state which ones help assess its reliability and which do not, justifying each response: known authorship, publication date,…
From this list of elements on a web page, state which ones help assess its reliability and which do not, justifying each response: known authorship, publication date, number of "likes", attractive design, cited sources, spelling mistakes.
An article shows two dates: "published on 3 March 2019" and "updated on 12 January 2026". Explain the difference between the two and which one you would check to decide…
An article shows two dates: "published on 3 March 2019" and "updated on 12 January 2026". Explain the difference between the two and which one you would check to decide if the information is up to date, giving an example of a topic where updates are crucial.
Many websites have an "About us" or "About" section. Explain three things you would check in that section before trusting the web page, and what you would suspect if…
Many websites have an "About us" or "About" section. Explain three things you would check in that section before trusting the web page, and what you would suspect if that section did not exist or were empty.
Write down three red flags that would make you doubt a web page at first glance (for example, a headline written to cause fear or shock), and give a made-up example of…
Write down three red flags that would make you doubt a web page at first glance (for example, a headline written to cause fear or shock), and give a made-up example of each.
You find an article written in 2012 titled "Cell phones of the future". Explain whether the date of publication affects its reliability and give two examples of topics…
You find an article written in 2012 titled "Cell phones of the future". Explain whether the date of publication affects its reliability and give two examples of topics where the date is crucial and one example of a topic where it hardly matters.
Types of sources and step-by-step filtering
Not all sources are worth the same. A primary source is the original testimony or document: your grandmother telling what her school was like, an official record, an interview, the data from a survey. A secondary source analyzes or summarizes primary sources: a history book, an encyclopedia, a news feature. Both are useful; what matters is knowing which one you have in front of you.
In general, for schoolwork the more trustworthy ones tend to be specialized encyclopedias, scientific journals, institutions (museums, universities, government agencies), and news outlets with an editorial team that signs and corrects its work. Less trustworthy: anonymous forums and videos with no author.
A collaborative online encyclopedia has advantages (it's free, very up to date, and usually cites sources) and risks (almost anyone can edit it, and there may be errors or temporary vandalism). Use it as a starting point: read the summary, follow the references it cites, and verify the important facts in those original sources.
For a project on the solar system, you have found these sources: a specialised encyclopaedia, an anonymous forum, a science museum website, a social media video with no…
For a project on the solar system, you have found these sources: a specialised encyclopaedia, an anonymous forum, a science museum website, a social media video with no known author, and an article in a scientific journal. Order them from most to least reliable and justify the order chosen.
To keep only the sources that are trustworthy, you can pass the results through a series of filters, as shown in the diagram, but one of the filters is covered up.…
To keep only the sources that are trustworthy, you can pass the results through a series of filters, as shown in the diagram, but one of the filters is covered up.
Propose the missing filtering question in the covered step and explain why it is important to apply it before using a source in a project.
Explain the difference between a primary source and a secondary source using this scenario: for a project about life in the 1960s, your grandmother tells you what her…
Explain the difference between a primary source and a secondary source using this scenario: for a project about life in the 1960s, your grandmother tells you what her school was like, and you also read a history book that summarises that era.
On a collaborative online encyclopaedia, almost anyone can edit articles. Explain the advantages and risks of this, and describe how you would use it correctly as a…
On a collaborative online encyclopaedia, almost anyone can edit articles. Explain the advantages and risks of this, and describe how you would use it correctly as a starting point for a project without relying on it completely.
Facts, opinions, and bias
Sources with a financial interest
Bias isn't always about teams: sometimes it's about money. If an article says "sponsored content," only highlights the advantages of a product, includes discount codes, or all its links lead to the store that sells it, the writer gains if you buy. That doesn't mean they always lie, but it is not an independent report: to cross-check, look for lab tests, consumer protection agencies (such as PROFECO), reviews from outlets with no ties to the brand, and opinions from specialists.
Be careful with correlations too: two things rising at the same time doesn't mean one causes the other (you'll see this in the cross-checking section). And be careful with famous people: personal experience is enough to tell what happened to that person (how a soccer player trains), but for health, science, or legal topics you need to turn to specialists with training and evidence.
Classify these four headlines as "fact" or "opinion" and justify each decision: (a) "The Lerma River is 930 kilometers long", (b) "The Lerma is the most beautiful river…
Classify these four headlines as "fact" or "opinion" and justify each decision: (a) "The Lerma River is 930 kilometers long", (b) "The Lerma is the most beautiful river in Mexico", (c) "Yesterday it rained 23 liters per square meter in Monterrey", (d) "Cities by the river are the best places to live".
A basketball match ends in controversy in the final minute. A newspaper from one city runs the headline "Scandalous theft in the final second", while the rival city's…
A basketball match ends in controversy in the final minute. A newspaper from one city runs the headline "Scandalous theft in the final second", while the rival city's newspaper headlines "Deserved victory in a thrilling finish". Explain what source bias is, how it is detected in this case, and how you would write a neutral summary of the match.
You are looking for information for a project on urban mobility and you find an article titled "Why this electric scooter is the safest on the market", signed by…
You are looking for information for a project on urban mobility and you find an article titled "Why this electric scooter is the safest on the market", signed by "Editorial Staff" and with a small tag at the end stating "Sponsored content by EcoScooters". The text only highlights advantages of the product and includes a link with a discount code to their store. Justify why this article lacks neutrality compared to an independent journalistic report, explain what biases it presents, and design a search strategy (with specific keywords, operators, or types of sources) to find the weak points or actual failures of that model.
The same content creator can be a good source for some topics and a poor one for others: a famous athlete speaking about training versus vaccines. Establish a criterion…
The same content creator can be a good source for some topics and a poor one for others: a famous athlete speaking about training versus vaccines. Establish a criterion to decide when someone's personal experience is sufficient as a source and when it is necessary to consult specialists, and apply it to two further examples.
Cross-checking with independent sources
To check a fact (for example, the population of your state), look for three sources that measured or collected the data on their own: the INEGI census, the state government, and an academic study. If they agree, you have real confirmation. If they differ, check the date and the method: two sources can give different values because they measured in different years, rounded differently, or used a different definition. This explains, for example, why one page gives one height for a volcano and another gives a slightly different value: look for the official source and stick with it, noting where you got it.
Data that doesn't say where it comes from
"80% of teenagers use AI for homework" is no good if it doesn't say where it comes from. To trace it, look for the name of the study or the institution, or the exact phrase in quotation marks. If you find the original, question it: how many people did they ask? Who (age, place)? When? Who paid for the survey? Without those answers, the number isn't reliable.
Domains aren't enough
Web addresses end in .edu (educational institutions), .gov (government), .org (organizations, often nonprofit), or .com (commercial). They give a clue, but guarantee nothing: anyone can register an .org for propaganda purposes, a .com can be an excellent news outlet, a university page can host a personal blog with no review, and a government site can be out of date.
Two web pages contradict each other regarding the height of Pico de Orizaba: one says $3715\ \text{m}$ and the other says $3718\ \text{m}$. Explain step by step how you…
Two web pages contradict each other regarding the height of Pico de Orizaba: one says $3715\ \text{m}$ and the other says $3718\ \text{m}$. Explain step by step how you would decide which figure to use in your project, and what might cause two sources to give different values.
Web addresses end in domain extensions such as .edu, .gov, .org, or .com. Explain what usually lies behind each of these domain extensions and reason why the domain…
Web addresses end in domain extensions such as .edu, .gov, .org, or .com. Explain what usually lies behind each of these domain extensions and reason why the domain extension alone does not guarantee that the information is reliable, giving an example for each case.
Cross-checking information does not mean finding it repeated on three websites, because those three websites may have copied it from the same incorrect source. Explain…
Cross-checking information does not mean finding it repeated on three websites, because those three websites may have copied it from the same incorrect source. Explain what it means for sources to be "independent", and describe how you would verify a statistic about the population of your province using three genuinely independent sources.
An article states: "80% of teenagers use AI to do their homework", without indicating where that figure comes from. Describe how you would try to track down the original…
An article states: "80% of teenagers use AI to do their homework", without indicating where that figure comes from. Describe how you would try to track down the original survey or study and what questions you would ask about that study (how many people were surveyed, who they were, when) before believing it.
A false statement appears copied, almost word for word, across twenty different websites. Explain why the fact that an idea is repeated in many places does not guarantee…
A false statement appears copied, almost word for word, across twenty different websites. Explain why the fact that an idea is repeated in many places does not guarantee that it is true, and describe how you would attempt to track down the original source of the statement.
A headline reads: "Ice cream consumption causes drownings: both rise together every summer". Explain the difference between correlation and causation, what third factor…
A headline reads: "Ice cream consumption causes drownings: both rise together every summer". Explain the difference between correlation and causation, what third factor explains this case, and write a correct headline that informs without misleading.
Disinformation and manipulated content
A reverse image search works the opposite way from a normal search: you upload the photo and the search engine shows you on which pages and dates it appeared before. If "this week's flood in your city" was already circulating six years ago in another country, the deception is exposed. Also, check whether any serious news outlet publishes the same thing, and look for the author or the original source of the image.
With deepfakes the problem is bigger: "seeing is believing" is no longer enough, because a video or audio clip can look perfect and still be fake. Before believing a surprising video of a well-known figure: (1) check whether serious news outlets or the person themselves confirm it, (2) look for odd details (voice, lips, blinking, shadows), and (3) trace the original source of the video and its date.
For a school news outlet that wants to publish that "the municipal library is closing," the protocol would be: consult official sources (notices from the municipality), ask the person in charge of the library and the corresponding authority directly, look for documents or announcements, and, if the versions don't match, not publish it as true: report only what is confirmed and say that the rest is being verified.
Back to the beginning: the "no classes tomorrow" message has no author, no date, and no source, and it asks you to forward it urgently. Before passing it on, check the notice on your school's official website or social media, or ask your teacher.
A photo of an impressive flash flood is circulating on social media, presented as "from this week in your town", but the image is actually from another country and six…
A photo of an impressive flash flood is circulating on social media, presented as "from this week in your town", but the image is actually from another country and six years ago. Explain what a reverse image search is, how it would help you uncover the deception, and what other two checks you would carry out.
A nutrition blog enthusiastically recommends a "miracle" smoothie, and all its links lead to the online store selling it. Analyse the reliability of that page taking…
A nutrition blog enthusiastically recommends a "miracle" smoothie, and all its links lead to the online store selling it. Analyse the reliability of that page taking into account authorship, potential financial interests, and the cited sources, and propose where you would cross-check the information.
Design a checklist of six to eight questions to evaluate any internet source. Then, make up a description of a specific web page (topic, author, date, appearance,…
Design a checklist of six to eight questions to evaluate any internet source. Then, make up a description of a specific web page (topic, author, date, appearance, adverts) and apply your checklist to it, stating your conclusion.
The school's digital magazine wants to publish news about an alleged closure of the local library. Design the verification protocol that the editorial team should follow…
The school's digital magazine wants to publish news about an alleged closure of the local library. Design the verification protocol that the editorial team should follow before publishing it: which sources to consult, whom to ask directly, and what to do if the accounts do not match.
On the high school's social network, a ten-second video goes viral where the mayor appears to announce that classes are suspended tomorrow due to an extreme cold wave.…
On the high school's social network, a ten-second video goes viral where the mayor appears to announce that classes are suspended tomorrow due to an extreme cold wave. Looking closely, the voice sounds metallic and the outline of the mouth shows a blurry flicker that does not match the pronunciation of certain words. Technically justify why these clues point to a "deepfake", predict what consequences sharing it without verifying would have, and design a three-step protocol that students should follow to verify the news before staying home.