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the amount by which you could be off. like if you estimate the height of something to be 50 feet with a margin of error of 5 feet, that means it could really be anywhere from about 45 to 55 feet
In real life measurements, there are always errors because of equipment inaccuracy, limitation of the measuring process, human error, etc etc. So no measurement can be considered pin point correct. In most scientific and technical measures, there is a range around which a measure might be.
One common way to express this is to give the most central or likely measure and a range, called the margin of error. An example would be measuring the length of something and saying that it is 1m +/- 1cm. This means that something is very likely between 99cm and 101cm long. This the margin of error. It is also common for that to be expressed in percentages.
Imagine you have a scale that can weigh you but only in 1 kilogram units;can’t go smaller. You can weigh yourself and get the number 71. You know your weight is between 70 and 72 kgs, you got a result with a margin of error of 1 kg.
Margin of error has a technical meaning when you’re talking about sampling.
Imagine you want to know how the proportion of red and black cards there are in a deck of playing cards, but you don’t want to look through every card. You shuffle the deck and draw out two cards. You get two red cards. So you estimate the deck is all red cards.
Now I think it’s obvious you haven’t drawn enough cards there to get a reliable estimate. If that were a normal deck and you pulled two random cards again (from a full deck) you’d have a 1 in 3 chance of getting the complete opposite result – two black cards!
You’d get a more reliable estimate by drawing 10 cards, and even more reliable estimate by drawing 20. If you drew all 52 cards you’d be 100% accurate.
But just *how* reliable are these estimates?
This is what the margin of error tells you. For a given level of “confidence” – most commonly 95% – it gives you a range and tells you a range – say, +/-10%. What this means is that if you repeated that sampling process multiple times, the true value would be within that range 95% of the time.
It’s a phrase that comes from written (and later, printed) text.
Pull up any document, written, printed, or digital (like a PDF or a Word doc). On just about any one of them, there will be a border all the way around the page where no text is written. That’s the margin. By convention, we leave it blank to make the page easier to read. If you want to be “correct”, you don’t write anything there.
However, if you *reeeeeeally* needed to just barely complete a word, and you don’t have enough room to fit the whole spelling inside the border, you *cooooould* fudge it out into the margin. Just this once. It’s not like it’s the edge of the paper, there’s still paper *there*, right? You’d prefer to not have to use the margin like that, but if it becomes necessary, it’s available to you.
And that’s basically the whole concept of a “margin of error”. If you are doing a thing where you’re expected to stay within some explicit range, and for a short moment you need to go a small ways outside of that range, you have a buffer zone that lets you do so. It’s technically an error to be outside the margin, but it’s not the end of the world.
Margin = edge (in this case we use it to mean limit)
Something within the margin of error = within an acceptable range or limit.
Any answers more complex than that are basically a sampling and statistics lesson.
This is a phrase that’s often used by pollsters. When you carry out a poll, you usually analyse it by assuming that your sampling method picks people perfectly at random – that is, everyone in the population is equally likely to be picked. Under these conditions, there is a predictable amount of randomness in the results of the poll, depending on the sample size – if you carry out exactly the same poll again you will typically get slightly different results just by chance, but this effect is more pronounced with smaller sample sizes. The margin of error quoted by pollsters is a measure of how big this variation is. Specifically, about 95% of the time, the results of the poll will be within the margin error of the true result. And the margin of error is roughly 1/sqrt(sample size).
However, in a real life poll there are additional sources of error. Your sampling method might be much more likely to pick some people than others, some people will refuse to participate, and some people will fail to give accurate answers. Instead of adding randomness to the results, these effects skew the results in certain directions. But it’s very difficult to measure or predict these effects, so the quoted “margin of error” generally doesn’t include any of them.
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