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Scatterplots and Correlations - Problem 1 4,256 views

Teacher/Instructor Alissa Fong
Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

This is a classic multiple-choice question that’s probably going to show up on one of your standardized test maybe in a high school x-exam on maybe even the SAT or ACT. Let's check it out.

Does this graph represents a positive correlation choice a negative correlation b or no correlation c? I’m kind of translating it into multiple choice teacher style.

Okay let’s check it out this graph represents soda prices what happened is this person went out into the real world and collected information on different stores how much they sell different sizes of soda for.

Like for example you guys probably know most of the time a can of soda is like 12 ounces, so if you look at ounces, 12 ounces costs about 40 cents at one place or about a $1.10 somewhere else. That’s how you interpret this graph.

We don’t care about that too much what we care about is the correlation. Remember positive means as one variable increases the other increases, negative means as one increases the other decreases no correlation means it’s like totally random we can’t tell.

Well if you look at this we have a trend that goes like that if I already draw a trend line it would have a positive slope, positive correlation, because as you increase the number of ounces the cost of how much you are paying also increases. That’s how you guys can determine correlation they go really quickly once you get the hang on the vocabulary.