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# Interpreting a trend line

The graph shows how studying affects test scores. The line slope of 15 means that for each extra hour of studying, there is usually a 15-point increase in test score. But it's not a guarantee. Some students may do better or worse than the trend. Created by Sal Khan.

## Want to join the conversation?

• Can someone please explain what bivariate data is ?
• Same as above, but maybe a better way to understand vocab:
bi = 2
variate = variables
• According to that line, if someone studied about 7 hours, then their score should be ~125 - which is off the chart. The maximum score appears to be 100, so what's going on? How can the line show that 7 hours is a score of ~125?
• The line doesn't go on infinitely (I guess it is technically a line segment). If you plotted more and more points and the hours went up and up the line would just level off. Remember that this is data taken from the real world. It doesn't have the precision most math has. If you have a line that is plotting the amount of money you pay for flowers and one flower is 2 dollars you can have an exact, perfect line. This type of data is not like that. If you have a student who studies for 10 hours he'll probably get in the 90s but it's not definite. The line is just an estimate.
• Hi moderators,

i noticed that the content in this video is repeated in another video in the same module "interpreting slope of a line". the content is same in both the videos.
• I am not sure if there is an easier way to go about this but there has to be some sort of formula. It is hard eyeballing the line and then it is even more difficult trying to measure a line on a computer screen........
• At , what does Sal mean?
• if the first statement were true, at x=0 (did not study), you would have seen a score of 15 --> (0,15) -> but there is no datapoint to indicate this, so this first statement is false/incorrect.
• Does line of best fit have to be exact? The line of best fit can also be used to find slope, so if you don't place the line of best fit perfectly, the actual slope maybe a bit off. How can I fix this kind of problem?
• Why is it important that for a best-fit line be drawn with an equal number of data points above and below the line?
• It isn't actually too important. It usually just turns out that way because it's the average line of the data points make.
• i understand nothing. literally.
• The more time is the more score
(1 vote)
• This isn't exactly a question about the video, but is it possible to determine the line of best fit without a graph? If you have several points, and no graph, how would you determine the equation of the line of best fit?
Thanks.