Video: Distinguishing between Population and Sample

Tim Burnham

Which is the most appropriate method for collecting data about the amount of salt in seawater? [A] Sample method [B] Mass population method.

02:43

Video Transcript

Which is the most appropriate method for collecting data about the amount of salt in seawater? A) The sample method or B) The mass population method.

Well first, let’s just recall what the mass population and sample methods are for collecting data. With the mass populated method, you gather data from every single member of the entire population. Now this tells you exactly what you want to know about the whole population. And it’s great when accuracy is really important. For example, if you were inviting 10 friends round for dinner, you’d want to ask all of them if they have any special dietary requirements. You need to ask every single one, not just a small sample. So remember, with a small population, it can be cheap and easy to analyse the whole thing, every member. But with a very large population, it might be impractical to do that even if you wanted to know the answer very accurately.

Now with the sampling method, you sample a small subset of the whole population and use the results from the data that you gather there to make estimates about the whole population. Now there’re various different ways of doing sampling, random samples, stratified samples, systematic samples, and others. But the point is, it’s much cheaper and easier to gather this data because there’s a lot less of it. But the downside is that you may have picked an unrepresentative sample. So the data that you end up analysing may not be typical of the population as a whole.

Right. Let’s get back to our question. If we want to know how much salt there is in seawater, are we gonna use a sampling method or are we gonna use a mass population method? Right. There’s getting off a one and a half billion cubic kilometres of seawater on the Earth; that’s over 300 cubic miles.

Imagine a cube, one mile wide, one mile long, and one mile high. Now imagine 300 million of those cubes. That’s a lot. It’ll be so difficult and so time consuming to measure how much salt was in all that water. And it would have such an enormous environmental impact, that surveying all the sea water on the Earth would be practically impossible. So by carefully choosing a series of samples from oceans and seas around the world, you could get a pretty good idea of the amount of salt in seawater, and scale this up to get a good estimate for the global total.

So for practical reasons, the sample method would be the most appropriate method in this particular case. So our answer is A) The sample method.

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