1. Please Turn to Yesterday's Handout

2. Time for Sugar to Dissolve
Experiment
Independent Variable
Dependent Variable
Control
Variable(s)
As you run to the store, how does your distance change with time?
Time
Distance
How does temperature affect how quickly a sugar cube will dissolve?
Temperature
Time for Sugar to Dissolve
Is there a relationship between human foot length and height?
Foot Length
(could go either way)
Height
What is the relationship between the world’s population and time?
Population
Is there a relationship between the maximum weight a person can bicep curl versus the maximum that a person can bench press?
Weight Person Can Bench Press
Weight Person Can Bicep Curl
Is there a relationship between the number of words on a page versus the area of a book cover?
Area of Book Cover
Number of Words on a Page

3. Dependent Variable (placed on vertical axis: y)
A dependent variable is a variable dependent on the value of another variable
Independent Variable (placed on horizontal axis: x)
The independent variable causes an apparent change in, or affects the dependent variable

4. Examples:
In a call centre, the number of customers serviced depends on the number of agents
At ski resort, the amount of sales, in $, depends on the amount of snow
The amount of bacteria on your hands depends on how often frequently you use hand sanitizer.
dependent variable (y)
independent variable (x)

5. A scatter plot shows a ____________ correlation when the pattern rises up to the right.
This means that the two quantities increase together.
A scatter plot shows a ____________ correlation when the pattern falls down to the right.
This means that as one quantity increases the other decreases.
A scatter plot shows _____ correlation when no pattern appears.
Hint:
If the points are roughly enclosed by a circle, then there is no correlation.
positive
negative no

6. Strong or Weak Correlation?
If the points nearly form a line, then the
correlation is ___________________.
If the points are dispersed more widely,
but still form a rough line, then the
correlation is _______________________.
strong
weak
Hint:
To visualize this, enclose the plotted points in an oval.
If the oval is thin, then the correlation is strong.
If the oval is fat, then the correlation is weak.

8. Does age have a strong positive correlation with height? Explain.
Do you think the variables are placed appropriately on the axes?
c) Would weight vs. age show a strong positive correlation?
d) Can you think of a variable that does have a strong positive correlation with age?
e) Can you think of a variable that has a strong negative correlation with age?

9. Line of
Best Fit
…affectionately known as LOBF

10. All about the LOBF… What is it? How do I draw it?
shows a trend or pattern on a scatterplot
used to make predictions
How do I draw it?
models the trend/pattern
models the trend/pattern
through as many points as possible
equal points above and below the line

11. Line of Best Fit trend pass equal
To be able to make predictions, we need to model the data with a line or a curve of best fit.
Guide for drawing a line of best fit:
1. The line must follow the ______________.
2. The line should __________ through as many points as
possible.
3. There should be ____________________________ of points
above and below the line.
4. The line should pass through points all along the line, not just
at the ends.
trend
pass
equal

12. Which one of these is the best LOBF?
And what is wrong with the others?
Line not in middle of points #1 #2
Doesn’t model trend #3 #4
Wrong for all kinds of reasons!

13. Return to front side of hand out and make lines of best fit on each of the given 6 graphs.

14. You can use LOBF’s to make predictions for values that are not actually recorded or plotted.
Interpolation
Extrapolation
prediction involving a point within the set of data
prediction involving a point outside the set of data
(line needs to be extended)

15. Fill in blanks on handout

16. Using our height and humerus data…
How tall would a person be that had a humerus of 44 cm?
181 cm tall
Extend the line!
Is this interpolation or extrapolation?
exptrapolation

17. Using our height and humerus data…
How long would a person’s humerus be that was 163 cm tall?
28 cm long
Is this interpolation or extrapolation?
interpolation

18. Makin’ sure you get it!
See bottom of handout