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Data collection and conclusions — Basic example

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- [Instructor] All right, we have a wordy question here. The global temperature anomaly indicates how much warmer or colder the average global temperature is than normal during a particular time. A researcher conducting an observational study charted and analyzed atmospheric carbon dioxide, CO2, levels, and the global temperature anomaly in degrees Celsius since the year 1960. The researcher observed that the rate of, okay, this is the part this seems to get interesting. The researcher observed that the rate of increase of atmospheric CO2, carbon dioxide, since 1960, approximately four percent per decade, is comparable to the rate of increase in the global temperature anomaly during the same time period, approximately 3.9% per decade. Based on this data, which conclusion is valid? All right, let's see. There is a correlation between the increase in atmospheric CO2 levels since 1960 and the increase in the global temperature anomaly during the same time period. That one seems pretty valid. These are both moving in the same direction together. That's what correlation tells us. It doesn't mean that necessarily the CO2 levels are causing the temperature increase or that the temperature increase is causing the CO2 levels to increase. It's just saying that look, over this time, we're seeing that these two things are moving together, which is what correlation is talking about. How much do these data points move together? So I'm kind of, I'm liking this one, I'm liking this one. So I'll, well actually, let me read all of them before I pick that choice. The increase in the global temperature anomaly since 1960 caused the increase in atmospheric CO2 levels during the same time period. Well no, we don't know that. We don't know whether there is causality here, whether, we haven't, just by looking at that data of these two things moving together, you can't say that the temperature caused the CO2 to move up. This is one of the classic things that a lot of times when two things correlate, people want to show that there's some causality. But it's much harder to show causality than it is to show correlation. So I definitely don't like that. The increase in atmospheric CO2 levels since 1960 caused the increase in global temperature anomaly during the same time period. Well that might be a reasonable hypothesis, but that data doesn't tell us that. It doesn't tell us, there might have been some other cause that caused both of those two things to go up. Or this might have just been two things that happened to move together but it wasn't, it wasn't because of any kind of causation one way or the other. So you can't say that just based on the data that we have, the fact that they both increased at roughly four percent per decade since 1960, you can't say that one caused the other. There is no correlation between the increase in atmospheric CO2 levels since 1960 and the increase in global temperature anomaly during the same time period. No, there for sure is a correlation. You would say there's no correlation if in some years, the CO2, some decades, CO2 went up and the, and the temperature went down, while in other decades, they both went up and in other decades, they both went down. That would be no correlation. If actually every time one of them went up, the other one went down, that would be a negative correlation. If they move together, that is just a very strong positive correlation, and no correlation would be if you couldn't, you know, sometimes when one moves up, the other one moves up or down, and when the other one moves up or down, the other one moves up or down. I don't know if that last thing I said just made sense. But there was definitely a correlation. They were moving together. They were both increasing, and roughly at the same rate, over per decade since 1960, so I would rule that one out. So yep, feel good with our first choice.