Statistics and probability
Statistical and non statistical questions
A statistical question is one that can be answered by collecting data and where there will be variability in that data. For example, there will likely be variability in the data collected to answer the question, "How much do the animals at Fancy Farm weigh?" but not to answer, "What color hat is Sara wearing?". Created by Sal Khan.
Want to join the conversation?
- In5:32, it is said that the question "Find the difference in rainfall in Seattle and Singapore in 2013" is not a statistical question. However, to find the amount of rainfall, you have to measure the rainfall on each day. It is data with variability, so shouldn't it be a statistical question?(16 votes)
- If the question asked to compare the total rainfall in 2013 to the average over that past five years, then that would be a statistical question. Look for key words for measures of central tendency and trends, rather than computation of exact amounts.(4 votes)
- Would a non-statistical question like, "What is 4x5?" become a statistical question if someone had the wrong answer?(5 votes)
- I believe it could be a statistical question if it were something like this:
"How many 3rd graders got the question, 'What is 4 x 5?' wrong on this year's state test compared to last year?"
These types of questions really depend a lot on the exact words used to express the question.(15 votes)
- Are categorical questions statistical questions? For example, "What are the color of eyes of the 6th grade class?" While the answer is qualitative rather than quantitative, and would use a bar graph rather than a histogram, is it still a statistical question since it has variability?(9 votes)
- If you just want to find out what the eye colours are regardless of the numbers of people who have those colours, like you go around and write down the colours you observe without counting the occurrences, it is not a statistical question. If you count the occurrences, for example, 15 people have green eyes, 20 people have brown eyes etc, then it becomes a statistical question. As you said, in the latter case, you can plot a bar graph to present your data.(2 votes)
- At7:17, is it only a statistical question if you mention "in 2013" before you added it in the last example, or can it be statistical either way?(4 votes)
- Without the in 2013, it is kind of a complicated case. You have to think about what you want to consider. if you say throughout the history of the schools or since 1800, then this does become a statistical question no matter how you look at it. However, considering other things (like in 2013), you have concrete numbers that you can check the difference of, making it not a statistical question(2 votes)
- Question 8 asks: "In general, will I use less gas driving at 55 than at 70 mph?" The instructor states that variability in road conditions and in automobiles mean this question is statistical, however the question asks if, in general, *I* will use less gas. Because I can only drive one automobile at any given time, all of the conditions of any given trip are constant regardless of the speed at which I drive and the only variable is my speed. If in all cases I would use less gas driving at 55 than at 70 mph, does this not mean that there is no variability in the outcomes and therefore this cannot be a statistical question? To put it a different way, because there will never be a time when I get into a car and say, "Hey! With this car and these road conditions I can save more gas driving at 70 than I would driving at 55", there is nothing to analyze. Hmm.. Or perhaps there is some rule of thumb which says that any time you see the words "In General" or "On Average", it is automatically a statistical question regardless of the particulars of the question? Such a rule should be stated explicitly. But then it would follow that the question "In general what base does the binary number system use?" would also be a statistical question (which it is not). For these reasons, question 8 can't be statistical. What do you think? Thanks.(4 votes)
- It is statistical because you drive the car multiple times, thus coming up with a set of numbers rather than just one.(2 votes)
- Hi Do statistical questions have an origin?(4 votes)
- When was this made? It's 2021(3 votes)
- If we want to draw a simple random sample from a population of 4000 items, how large a sample do we need to draw if we desire to estimate the per cent defective within 2 % of the true value with 95.45% probability.(2 votes)
- I like how I see that people from seven years ago get comments from like 9 months ago. it's like, I don't think they're gonna respond.(2 votes)
- why does this involve math(2 votes)
What I want to do in this video is think about the types of questions that we need statistics to address and the types of questions that we don't need statistics to address. We could call the ones where we need statistics as statistical questions. And I'll circle the statistical questions in yellow. I encourage you to pause this video and try to figure this out yourself first. Look at each of these questions, and think about whether you think you need statistics to answer this question or you don't need statistics, whether these are statistical questions or not. I'm assuming you've given us a pass at it. Now we can go through this together. This first question is, how old are you? So we're talking about how old is a particular person. There is an answer here, and we don't need any tools of statistics to answer this. So this is not a statistical question. How old are the people who have watched this video in 2013? Now this is interesting. We're assuming that multiple people will have watched this video in 2013, and that they're not all going to be the same age. There's going to be some variability in their age. One person might be 10 years old. Another person might be 20. Another person might be 15. So what answer do you give here? Do you give all of the ages? But we want to get a sense of in general. How old are the people? So this is where statistics might be valuable. We might want to find some type of central tendency, an average a median age for this. So this is absolutely a statistical question. And you might already be seeing kind of a pattern here. The first question, we were asking about a particular person. There was only one answer here. There's no variability in the answer. The second one, we're asking about a trait of a bunch of people, and there's variability in that trait. They're not all the same age. And so we'll need statistics to come up with some features of the data set to be able to make some conclusions. We might say, on average, the people who have watched this video in 2013 are 18 years old, or 22 years old, or the median is 24 years old, whatever it might be. Do dogs run faster than cats? Once again, there are many dogs and many cats, and they all run at different speeds. Some dogs run faster than some cats, and some cats run faster than some dogs. So we would need some statistics to get a sense of in general or on average how fast do dogs run and then maybe on average how fast do cats run. Then we could compare those averages, or we could compare the medians in some way. So this is definitely a statistical question. Once again, we're talking about, in general, a whole population of dogs, the whole species of dogs, versus cats. And there's variation in how fast dogs run and how fast cats run. If we were talking about a particular dog and a particular cat, well, then there would just be an answer. Does dog A run faster than cat B? Well, sure. That's not going to be a statistical question. You don't have to use the tools of statistics. And this next question actually fits that pattern. Actually, no, this fits the pattern of the previous one. Do wolves weigh more than dogs? Once again, there are some very light dogs and some very heavy wolves. So those wolves definitely weigh more than those dogs. But there's some very, very, very heavy dogs. And so what you want to do here, because we have variability in each of these, is you might want to come with some central tendency. On average, what's the median wolf weight? What's the average, the mean wolf weight? Compare that to the mean dog's weight. So once again, since we're speaking in general about wolves, not a particular wolf, and in general about dogs, and there's variation in the data, and we're trying to glean some numbers from that to compare, this is definitely a statistical question. Does your dog weigh more than that wolf? And we're assuming that we're pointing at a particular wolf. Now this is the particular. We're comparing a particular dog to a particular wolf. We can put each of them on a weighing machine and come up with an absolute answer. There's no variability in this dog's weight, at least at the moment that we weigh it, no variability in this wolf's weight at the moment that we weigh it. This is not a statistical question. I'll put an x next to the ones that are not statistical questions. Does it rain more in Seattle than Singapore? Once again, there is variation here. And we would also probably want to know, does it rain more in Seattle than Singapore in a given year, over a decade, or whatever? But regardless of those questions, however we ask it, in some years, it might rain more in Seattle. In other years, it might rain more in Singapore. Or if we just picked Seattle, it rains a different amount from year to year. In Singapore, it rains a different amount from year to year. So how do we compare? Well, that's where the statistics could be valuable. There's variability in the data. So we can look at the data set for Seattle and come up with some type of an average, some type of a central tendency, and compare that to the average, the mean, the mode-- the mode probably wouldn't be that useful here-- to Singapore. So this is definitely a statistical question. What was the difference in rainfall between Singapore and Seattle in 2013? Well, these two numbers are known. They can be measured. Both the rainfall in Singapore can be measured. The rainfall in Seattle can be measured. And assuming that this has already happened and we can measure them, then we can just find the difference. So you don't need statistics here. You just have to have both of these measurements and subtract the difference. So not a statistical question. In general, will I use less gas driving at 55 miles an hour than 70 miles per hour? This feels statistical, because it probably depends on the circumstance. It might depend on the car. Or even for a given car, when you drive at 55 miles per hour, there's some variation in your gas mileage. It might be how recent an oil change happened, what the wind conditions are like, what the road conditions are like, exactly how you're driving the car. Are you turning? Are you going in a straight line? And same thing for 70 miles an hour. When we're saying in general, there's variation in what the gas mileage is at 55 miles an hour and at 70 miles an hour. What you'd probably want to do is say, well, what's my average mileage when I drive at 55 miles an hour and compare that to the average mileage when I drive at 70. So because we have this variability in each of those cases, this is definitely a statistical question. Do English professors get paid less than math professors? Once again, all English professor don't get paid the same amount, and all math professors don't get paid the same amount. Some English professors might do quite well. Some might make very little. Same thing for math professors. So we'd probably want to find some type of an average to represent the central tendency for each of these. Once again, this is a statistical question. Does the most highly paid English professor at Harvard get paid more than the most highly paid math professor at MIT? Well, now we're talking about two particular individuals. You could go look at their tax forms, see how much each of them get paid, especially if we assume that this is in a particular year. Let's just make it that way, say in 2013, just so that we can remove some variability that they might make from year to year, make it a little bit more concrete. If this was does the most highly paid English professor at Harvard get paid more than the most highly paid math professor at MIT in 2013, then you have an absolute number for each of these people. And then you could just compare them directly. So when we're talking about a particular year, particular people, then it isn't a statistical question.