Ch. 14 – Scatter Plots HOW CAN YOU USE SCATTER PLOTS TO SOLVE REAL WORLD PROBLEMS?

Vocabulary  __________________– two sets of data usually represented by the x and y value.  _________________– a graph with points plotted that show the relationship between two sets of data  _______________ – a set of closely grouped data, either in a group or along a line.  _____________– a data point that is very different from the rest of the data in the set.  _______________– describes how sets of data are related. Positive association, negative association, or no association.  ______________ - a straight line that comes closest to the points on the scatter plot. Cluster Association Outlier Bivariate Data Scatter Plots Trend Line

Flip to page 433 in text A. Making a Scatter Plot  Answer/Discuss question A – (Look at the table given)  Sample Answer: A greater number of study hours are likely to be associated with higher test grades.  Answer/Discuss question B – (Make a scatter plot)  Reflect/Discuss:  1. What trend do you see?  Test scores increase as the number of hours studied increases.  2. Do you think if someone studied for 10 hours, that it would be reflected on the graph?  No, the scores that someone can get on a test does not exceed 100.

Interpreting Clusters  A – Describe the clusters that you see:  There are clusters around the 50 minute and 80 minute interval.  B - What do the clusters tell you about the eruptions of Old Faithful? (look at time)  There are short wait times follow by shorter eruptions and longer wait times followed by longer eruptions.  C – Describe any outliers you see in the scatter plot.  The point near (57, 3) appears to be an outlier because it does not fall into either cluster.

Association – How are the data related?  ____________________– data that increases together  ____________________– data that decreases together  ____________________– no relationship between the two data sets.  Positive and negative associations have data that typically lie along a line which exhibits a _______________________.  Data that does not lie along a line, typically exhibit a _______________________.  YOUR TURN – pg. 435 #6.  Work on page 436 #1-4 Positive association linear association no association Negative association nonlinear association

Making Predictions with Trend Lines  Pg. 439 A – Make a scatter plot of Joyce's running data. B – Draw a Trend Line – HINT – Start at (0,0) – Draw a line with About the same number of points above and below the line. C – Use the line to make a predictions (To get as close as possible) ** If all points are close to the trend line then you have a ___________ linear association. strong

Finding Equation of Trend Line Use _______ points on your trend line to find the slope and write the equation in slope intercept- form; 1. Find the Slope of Trend Line  Hint: You can also use rise/run to find the slope of your trend line. 2. Find the y-intercept of line using 1 ________________ and ____________. 3. Use the slope and y-intercept to write the equation in slope-intercept form two slopecoordinate

Pick Coordinates on Trend Line (100,5) (200,10) Find the Slope: M = _______________ = = Find y-intercept: y=mx+b, (100,5) 5 = 1/20(100) + b 5 = 5 + b -5 0 = b Plug into Formula: Y = 1/20x Not an exact equation due to us using a trend line

 Class Work – Book work -  Homework: Worksheet Both Sides