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Lesson 2: Interpreting scatter plots

# Example of direction in scatterplots

There are two graphs. One shows the relationship between study time and test grades. Do you get better grades if you study more? The other graph shows the relationship between shoe size and grades. Do you get better grades if you wear larger shoes? Created by Sal Khan.

## Want to join the conversation?

• In to , when he is explaining the answers, one of them says there's a nonlinear relationship, and then it says there is no relationship in another answer. Do these things mean the same thing?
• No, these are not the same thing. "No relationship" is when the points are all over the place and there isn't any type of correlation like between your shoe size and how many computers you have in your house. But, a nonlinear relationship is when the points have a correlation but not a linear correlation, maybe it has a exponential correlation. For example, you are monitoring growth of a country's population, let's say on day one, the country has x amount of people. Each day, the amount of people doubles. If you plot it, you find it is not a linear relationship or a "no relationship", but it is an exponential equation. Nonlinear relationship is when it is a relationship, but not linear. No relationship is when there is not any relationship between the points what so ever.

I hope that helped!
• Yeah, scatterplots are used to show raw data and the direction in them shows trends, which can be used to make decisions.
• so if you can fit a line, the scatter plot would be considered positive?
• Not necessarily. A line which has a slope >0 is positive, a line with slope <0 is negative.
• When Will I use this in real-life situations?
• Well obviously, you need to be in school more because that capital W is not grammatically correct.
• how can u tell its a positive line or a negative line
• x is generally thought of as the independent variable that affects the y variable, thus you always consider how x moving forward affects y.
• Can someone walk me through this again, please?
• Hi!

In the problem, two graphs are shown: one showing the relationship between study time and grades (the first graph), the other showing the relationship between shoe size and grades (the second graph).

Here are the possible answers and why they or why they don't work:

1. There's a negative linear relation between the study time and score, and a positive linear relationship between shoe size and score.

A negative linear relation is one where the y-values of the dots are generally decreasing as x increases. Since this is the opposite of what's happening with the first graph, this is not the answer.

2. There is a nonlinear relationship between study time and score and a negative linear relationship between shoe size and score.

The first graph is linear, while the second plot is not linear at all. This is also incorrect.

3. There is a positive linear relationship between study time and score and no relationship between shoe size and score.

This is true. The y-values of the first chart are generally increasing, while the values of the second plot do not follow a line.

4. Both graphs show positive linear trends of approximately equal strength.

The second graph is not linear at all, so this is not true.

Hope this helps!😄
• what does this mean so confused
• you are just trying to see if there is a relationship , in the example the more you study the better grades so it makes sense. whereas shoe size will be random
• How do you know if its independent or dependent