yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Example estimating from regression line


3m read
·Nov 11, 2024

Lizz's math test included a survey question asking how many hours students spent studying for the test. The scatter plot below shows the relationship between how many hours students spend studying and their score on the test. A line was fit to the data to model the relationship. They don't tell us how the line was fit, but this actually looks like a pretty good fit if I just eyeball it.

Which of these linear equations best describes the given model? So as you know, this point right over here shows that some student at least self-reported they studied a little bit more than half an hour, and they didn't actually do that well on the test. Looks like they scored a 43 or 44 on the test.

This right over here shows, or like this one over here, is a student who says they studied two hours, and it looks like they scored about a 64 or 65 on the test. This over here, or this over here, looks like a student who studied over four hours, or they reported that, and they got, looks like, a 95 or 96 on the exam.

And so then, these are all the different students; each of these points represents a student. They fit a line, and when they say which of these linear equations best describes the given model, they're really saying which of these linear equations describes or is being plotted right over here by this line that's trying to fit to the data.

So essentially, we just want to figure out what is the equation of this line. Well, it looks like the Y intercept right over here is 20, and it looks like all of these choices here have a y intercept of 20, so that doesn't help us much. But let's think about what the slope is. When we increase by one, when we increase along our x-axis by one, so change in X is one, what is our change in y?

Our change in y looks like, let's see, we went from 20 to 40. It looks like we got went up by 20, so our change in y over change in X for this model, for this line that's trying to fit to the data, is 20 over one. So this is going to be our slope, and if we look at all of these choices, only this one has a slope of 20, so it would be this choice right over here.

Based on this equation, estimate the score for a student that spent 3.8 hours studying. So we would go to 3.8, which is right around, let's see, this would be 3.8, would be right around here. So let's estimate that score. If I go straight up, where do we intersect our model? Where do we intersect our line?

So it looks like they would get a pretty high score. Let's see, if I were to take it to the vertical axis, it looks like they would get about a 97. So I would write my estimate is that they would get a 97 based on this model.

Once again, this is only a model; it's not a guarantee that if someone studies 3.8 hours they're going to get a 97, but it could give an indication of what maybe might be reasonable to expect, assuming that the time studying is the variable that matters.

But you also have to be careful with these models because it might imply, if you kept going, that if you study for nine hours, you're going to get a 200 on the exam, even though something like that is impossible. So you always have to be careful extrapolating with models and keep it, take it with a grain of salt.

This is just a model that's trying to fit to this data, and you might be able to use it to estimate things or to maybe set some form of an expectation, but take it all with a grain of salt.

More Articles

View All
Types of mixtures | Intermolecular forces and properties | AP Chemistry | Khan Academy
I suspect that you might already be familiar with the term “mixture.” It really does mean what you think it means. If you take two or more substances and you were to mix them together, you are dealing with a mixture, and it could be a solid, a liquid, or …
Bringing Life-Changing Treatments to the Blind in India | National Geographic
The world is invisible to the blind people, but at the same time, the blind people withdraw themselves from the surrounding, and they make them invisible. Unless the people who are cited actively try to find them out, they will remain in the dark. [Music…
Creativity break: how do you get into your creative zone? | Khan Academy
[Music] I allow my brain to do the work to get into my creative zone when I have a problem to resolve. Sometimes I just sleep on it, and I let my subconscious mind work through resolving problems and solving problems. Our brains are always at work, like …
Generalizabilty of survey results example | AP Statistics | Khan Academy
Niketi took a random sample of 10 countries to study fertility rate and life expectancy. She noticed a strong negative linear relationship between those variables in the sample data. Here is computer output from a least squares regression analysis for usi…
Calculating a z statistic in a test about a proportion | AP Statistics | Khan Academy
The mayor of a town saw an article that claimed the national unemployment rate is eight percent. They wondered if this held true in their own town, so they took a sample of 200 residents to test the null hypothesis. The null hypothesis is that the unemplo…
YC SUS: Eric Migicovsky hosts founder office hours
All right, hi everyone. Um, my name is Eric Mikowski. I’m the course facilitator here at Startup School. Um, excited to do another round of online office hours with companies in Startup School. So, office hours, um, for those that might be tuning in for …