Success Criteria: Explanatory and Response Variables
A teacher has created a new lesson to decrease student anxiety in public speaking situations. She designs an experiment to test if her new lesson works better than the old lesson. Public speaking students are randomly assigned to receive either the new or old lesson; their anxiety levels during a variety of public speaking experiences are measured. Level of anxiety is the ____________ variable.
Quantitative
How we describe where the line is heading, e.g. either "up the hill" or "down the hill"
Direction
An r value of 0 indicates _____ ________________.
No correlation
A scatterplot that mixes up the explanatory and response variables will still show the correct r value.
(a) True
(b) False
(c) It depends
(a) True
A researcher finds that there's a relationship between how much sunlight a plant gets and the height it eventually reaches. She sets up an experiment with dim, medium, and bright lights for her plants. The explanatory variable is ________.
The level of light
The part of a scatterplot we place through the points (either by hand or with technology) that minimizes the "over" and "under" errors between points and line.
Line of best fit
How we describe how well the line approximates the data points, in other words, the closeness of the data points to the line of best fit.
Strength
Correlation always lies between these two numbers
-1 and 1
Most scatterplots we use in introductory statistics are linear in form; however, they could also have a form that is ______________.
Appropriate responses include:
Curved
Logarithmic
Exponential
A group of middle school students wants to know if they can use height to predict age. They take a random sample of 50 students at their school and record each student's height and age. Student age is the _________ variable.
Explanatory
The scatterplot with the following information
y = -1.2334x + 8.5031 and r = -0.9947
has what direction for the line of best fit?
Negative
What we call those points that are way outside the pattern of the line of best fit.
Outliers
The correlation coefficient only gives information about the _______ and _______ of a best fit line. It says nothing about form or outliers
direction and strength
The explanatory variable was first introduced to us in Algebra I as the ________________ variable.
Independent
Students' test grades increase along with an increase in number of minutes spent studying. The response variable must be _________.
Students' test grades
The scatterplot with the following information
y = -1.2334x + 8.5031 and r = 0.9947
has what strength for the correlation?
Very strong
Describe DOFS for the following scatterplot
D - positive
O - none
F - linear
S - strong
Correlation is
(a) resistant
(b) not resistant
(c) we can't use this term to describe correlation
(b) not resistant
Does this scatterplot mean that importing lemons from Mexico improves highway safety? Explain
No, just because there's a relationship or association between two variables, doesn't mean one causes the other.
Correlation does not imply causation!
The ___________ variable is the result of a study where the independent variable is manipulated. It is a factor whose variation is explained by the other factors.
Response
The name for the use of a regression line for prediction far outside the interval of values of the explanatory variable x used to obtain the line.
Extrapolation
Describe DOFS for the following scatterplot
D - negative
O - One, at around (24, 0.6)
F - linear
S - moderate
Estimate the r value (to the tenths place) of the following scatterplot
Around -0.8
There is a well-known example of rates of violent crime increasing when ice cream sales also increase. Does this mean increased ice cream sales cause murders?
No, just because there's a relationship or association between two variables, doesn't mean one causes the other.
Correlation does not imply causation!