# Scatter Plots for Bivariate Data Worksheets

Scatter plots are plotted on Cartesian Coordinate (x, y) graphs to help us examine the nature of a possible relationships between two data sets. You may also hear them referred to as scatter charts and scatter graphs. The individual positions that we plot out represent a single data point. When we look at all the data points as a whole, we can spot trends and possible correlational relationships. Students often have difficult understanding which variable should be plotted on which axis (horizontal (x) or vertical (y)). The variable that we change in the experiment is called the independent variable and it should always be plotting on the horizontal axis. The other variable is referred to as dependent and it should be found on the vertical axis. When we are analyzing scatter plots we are trying to identify some type of pattern. This can come in many forms. The data can be consistently increasing or decreasing this would indicate that the variables have a linear relationship. The data can also rise and then fall or vice versa and this indicates a nonlinear relationship. The data can also be all over the place showing that no relationship exists. These worksheets and lessons are helpful for students to learn how to plot data points in a scattergram and interpret the trends of the data.

### Aligned Standard: Grade 8 Statistics & Probability - 8.SP.A.1

- Correlating Test Scores Step-by-Step Lesson- If you score well on one test, does that indicate that you will score well on a test from a different subject?
- Guided Lesson - We look at a wide assortment of data to see if we find any concrete relationships.
- Guided Lesson Explanation - Gender based populations, cracker and light sales, and the fluctuating weight of two people.
- Independent Practice - If you complete all the problems on these three pages, you will need a good hour to work on them.
- Matching Worksheet - Match the associations to the data tables that they explain.

- Answer Keys - These are for all the unlocked materials above.

### Homework Sheets

We're looking for trends and relationships in data via graphs

- Homework 1 - A scatter plot shows a positive trend if y tends to increase as x increases or y tends to decrease as the x decreases. A scatter plot shows a negative trend if one value tends to increase and the other tends to decrease. A scatter plot shows no trend if there is no obvious pattern.
- Homework 2 - The data below is for 8 fruits shops. The data shows the number of sales of mangoes and oranges at 8 shops. Describe the association between the sales of mangoes and oranges.
- Homework 3 - Alan and Jordon took their weight on the first day of each Christmas for 7 years. Describe the association between the weight of Alan and Jordon.

### Practice Worksheets

All the files here are very large.

- Practice 1 - The chart shows the number of cell phones and tablets purchased by 9 groups of people.
- Practice 2 - The food committee followed the lunch habits of 10 students. The chart displays the number of times they had sandwiches and burgers for lunch.
- Practice 3 - Mrs. Julia runs the air conditioning and fan throughout the day to stay cool. She charts the monthly electric bill caused by the fan and A.C. Describe the association between the cost of electric for the fan and A.C.

### Math Skill Quizzes

The explanation and graphs are large here too.

- Quiz 1 - The population survey data for 5 years shows the number of goldfish and star fish. Describe the association between the population of goldfish and star fish.
- Quiz 2 - The population survey data for 5 years shows the number of baseballs and basketballs. Describe the association between the baseballs and basketballs.
- Quiz 3 - The data for 5 days shows the sale of toy cars and dolls. Describe the association between the sale of toy cars and dolls.

### How to Make Scatter Plots for Bivariate Data

Scatter plots are a very useful tool for visually representing data, especially bivariate data. It is that type of data where there are two variables, and each value of both the variables is paired. A scatter plot is used to display the relationship between these variables, and the shape of the plot then determines the type of the relationship.

The scatter plot uses the cartesian (x, y) coordinates to plot the variables. The common forms of relationships between two variables that a scatter plot can help in determining includes linear, non-linear, constant variance, and random. We first must collect the data.

**Step 1: Identify the independent and the dependent variables in the data.**

**Step 2: Mark the independent values on the horizontal axis and the dependent values on the vertical axis. **

** Step 3: Start plotting the paired values (x,y) .**

The shape you achieve at the end of plotting will determine the relationship between the two variables. You may have a few data points that do not follow these trends and it is okay to ignore these values. They are called outliers.