Bellwork August Copy and answer. Have Girls vs. Boys Handout on Desk  What type of sample is each of the following?  1. If you mail a questionnaire to 100 randomly selected students at a school? Random sample  2. If you survey 20 people as they walk past you on the street. Convenience sample  3. You survey visitors to a political website in order to predict the winner of an upcoming election. Biased sample

Girls vs. Boys  How do populations and samples fit in with central tendencies in the girls vs. boys lab?

Unit 1 Chapter 7 Section 9 Scatter Plots Pg. 416

EQ:  What is the difference between positive correlation, negative correlation, and no relation in scatter plots?

What is a scatter plot? Video Clip  Correlation is the relationship of two or more things, parts, etc.  WRITE DOWN 1 FACT FROM THE VIDEO CLIP.

Definitions:  Scatter plot: a graph with points plotted to show a possible relationship between two sets of data  Negative correlation: two data sets have a negative correlation if one set of data values increase while the other decreases  positive correlation: two data sets have a positive correlation when their data values increases or decreases together  no correlation: two data sets have no correlation when there is no relationship between their data values

To find out if two sets of data may be related, you can make a scatter plot of the data values in each set. A scatter plot has two number lines, called axes—one for each set of data values. Each point on the scatter plot represents a pair of data values. These points may appear to be scattered or may cluster in the shape of a line or a curve.

Correlations There are three ways to describe data displayed in a scatter plot. Positive Correlation The values in both data sets increase at the same time. Negative Correlation The values in one data set increase as the values in the other set decrease. No Correlation The values in both data sets show no pattern.

Practice

Steps for creating a scatter plot 1. Determine the scale and interval for each axis 2. Plot the point for each pair of values 3. Label the axes and the graph

Example 1 Use the data to make a scatter plot. Describe the relationship between the data sets. Type U.S. Only Rest of World Mammals Birds Reptiles Amphibians 10 8 Fishes Clams 61 2 Number of Endangered Species U.S. Rest of World Number of Endangered Species There appears to be no relationship between the data sets.

1940 8, , , , , ,864 Number of farm workers in thousands Year Example ,000 8,000 6,000 4,000 2,000 Use the data to make a scatter plot. Describe the relationship between the data sets. Year Number (in thousands) Number of Farm Workers The number of farm workers decreased from 1940 to 1970, which creates a negative correlation.

Example 3 Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain. The graph shows that as area increases, population increases. So the graph shows a positive correlation between the data sets.

Example 4 Write positive correlation, negative correlation, or no correlation to describe each relationship. The graph shows that as the length of string increases, frequency decreases. So the graph shows a negative correlation between the data sets. vps = vibrations per second

Example 5 Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain. The number of vacation days is not related to height. So there would not be any correlation between these two variables. height and number of vacation days

Work Session- A Sport with Teeth  A scatter plot shows the relationship between 2 quantities.  Look at the scatter plot on your handout.  Use the scatter plot on your paper to answer the questions.  Read each question carefully.  Good Luck!

Closing- Positive, Negative, or No Correlation? Negative Positive