MATH 147 - Chapter 6 (vocab)

How to determine whether a variable is the explanatory variable or the response variable? Which axis is each variable on

• The explanatory variable is the variable that explains why something happens. It is on the x axis

• The response variable is the response or result of the explanatory variable. It is on the y axis

• Ex: If this thing happens (explanatory variable), then as a result, this thing then happens (response variable)

How to determine if a scatter plot has a positive association or negative association

• Positive association: if the dots form a straight diagonal line going up

• Negative association: if the dots from a straight diagonal line going down

How to determine if a scatter plot has no association?

If the dots form a shape that is neither linear nor curved. They are scattered all over the place

How to tell if a scatter plot has a linear association or non-linear association

• linear association: when the dots form a straight line

• non-linear association: when the dots do not form a straight line (so they could form a curved line or are scattered all over the place)

How to determine if two variables have a positive association or negative association

• Positive association: If one variable increases, then so does the other. If one variable decreases, so does the other

• Negative association: If one variable increases, the other one decreases and vice versa

What does it mean if a scatter plot has a strong association, moderate association, or weak association

• Strong association: the dots are very close to each other

• Moderate association: the dots are kind of close together

• Weak association: the dots are not close together

How to determine whether two variables have strong association, moderate association, or weak association

• strong association: if only those two variables directly affect each other (nothing else)

• moderate association: if those two variables affect each other other and other factors can also affect the variables

• weak association: the two variables do not affect each other

How to determine if the correlation, r has the following:

1. positive association or negative association

2. strong association, weak association, or moderate association

1. 
   

• the correlation has a positive association if r is positive 

• the correlation has a negative association if r is negative

2. 
   

• the correlation has a strong association if r is close to 1 or -1. 

• the correlation has a weak association if r is close to 0. 

• the correlation has a moderate association if r is close to 0.5 or -0.5

Is correlation affected by scaling (multiplying)

• for example, could you double or triple correlation

no

Does correlation have units (like feet, inches, dollars, fahrenheit, etc..)

no

If a scatter plot is non-linear (curved or scattered all over), what is the correlation, r

near 0

What does it mean when it is asking for the strength?

Whether there is a strong, moderate, or weak association

What does it mean when it is asking for the form?

whether there is a linear association or non-linear association

What does it mean when it is asking for the direction?

Whether there is a positive or negative association

can outliers cause a dramatic change in the correlation

yes

when is it only acceptable to determine if the correlation, r is strong, weak, or moderate 

if the scatter plot is linear (not curved or scattered)

1. Can you determine if the correlation is strong, weak, or moderate if the scatter plot is linear?

2. Can you determine if the correlation is strong, weak, or moderate if the scatter plot is non linear (curved or randomly scattered)?

1. yes

2. No