PRE-ALGEBRA

PRE-ALGEBRA

Lesson 12-5 Warm-Up

2. The mode is ____.

3. The median is ____.

4. How many 8th grade students finished the race in less than 35 sec.?

5. How many 8th grade students finished the race in less than 33 sec.?

1. Complete the stem-and-leaf plot for the following data. ____.

PRE-ALGEBRA

Scatter Plots (12-5)scatter plot: a graph of ordered pairs (first quadrant of graph) that is used to show the relationship between two sets of data. It’s called a scatter plot, because the data looks scattered (spread) out all over the graph, but if you look at the data closer, you’ll see a pattern, or correlation.

Example: Use the table below to make a scatter plot of location comparing cities by latitude (distance from equator) with their average temperature.

What is a “scatter plot”?

How do you make a scatter plot?

PRE-ALGEBRA

Scatter Plots (12-5)Step 1: Draw a the first quadrant (+, +) of a coordinate grid. Label the x-axis with the name (title of the column in a table) of one of the sets of data and the y-axis with the name of the other set of data you’re comparing in a table. Be sure to scale the axes so that the values in both data sets will fit and mark numbers at appropriate intervals. Also, title your graph with what’s being compared.

Step 2: Treating one set of data as the x’s and the other set as the y’s, plot the data as ordered pairs. [Example: Latitude is 34 = Temp. of 61 can be made into the ordered pair (34, 61)

Analysis: As you can see, there is a correlation (relationship or pattern) between location and temperature. The higher the latitude (further away from the equator), the lower (colder) the temperature, and vice-versa, the lower the latitude (closer to the equator), the higher (warmer) the temperature.

PRE-ALGEBRA

Use the table to make a scatter plot of the elevation and

precipitation data.

Atlanta, GA

Boston, MA

Chicago, IL

Honolulu, HI

Miami, FL

Phoenix, AZ

Portland, ME

San Diego, CA

Wichita, KS

Elevation Above Sea Level (ft)

1,050

20

596

18

11

1,072

75

40

1,305

CityMean Annual

Precipitation (in.)

51

42

36

22

56

8

44

10

29

LESSON 12-5

Additional Examples

Scatter Plots

PRE-ALGEBRA

Scatter Plots (12-5)trend – a correlation, or relationship, between two data sets

A “positive slope” (value go up the further away from 0 on the x-axis) suggest a positive correlation (as one set of values increases, the other set tends to increase as well), a “negative slope” (value go down the further away from 0 on the x-axis) suggest a negative correlation (as one set of values increases, the other set tends to decrease, or do the opposite), and no obvios slope (the values are scattered and show no trend) suggest no relationship.

 

What is a “trend”?

How can you spot a trend?

PRE-ALGEBRA

Scatter Plots (12-5)Example: The following graph shows the Gold medal winning times in the Men’s 110-Meter hurdles in the Olympics form 1952 to 2004. Is there a trend? Explain?

Analysis: Since 1952, the winning times have generally decreased (gone down), so the trend seems to be negative, or there tends to be a negative correlation between the time in years and winning times (they’re getting smaller, or faster, over time).

PRE-ALGEBRA

Use the scatter plot below. Is there a positive correlation,

a negative correlation, or no correlation between temperatures

and amounts of precipitation? Explain.

The values show no relationship.

There is no correlation.

LESSON 12-5

Additional Examples

Scatter Plots

PRE-ALGEBRA

Answer the following questions based on the graph.

1. What do you know about the student at point A?

2. How many students read 3 books per month?

3. Is there a positive correlation, a negative correlation, or no correlation between books read and semester grades?

read 2 books per month, grade: 80

positive correlation

3

LESSON 12-5

Scatter Plots

Lesson Quiz