## Using Straight Lines to Model Relationships

#### Aligned To Common Core Standard:

**Grade 8 Statistics & Probability ** - 8.SP.A.2

How Can Straight Lines Be used to Model Relationships Most of the time, when we have to determine a relationship between two quantities, we use different graphs to illustrate the relationship. As simple as it may sound, straight lines can actually work for many quantities to demonstrate the relationship. When we have a problem involving two quantities, we look to find a hidden relationship between them. We determine either a relationship exists between the quantities or not. In case the variables are linearly related to each other, you can use a straight line to demonstrate their relationship on a graph. Use the line equation to find out the values of the two variables (x and y). For example, you have a straight-line equation y = 23.5 + 2.45x This equation is used to define the relationship between the length of a shoe length and the height of a person. Here x represents shoe length, and y represents the height. To find out the height of the man who has a shoe size 10, substitute the value 10 for x in the equation and predict the value of y. Plot the points on the graph. A rising line indicates a positive relationship between the variables, whereas a tumbling line indicates that there is a negative relationship between the variables. These worksheets and lessons help students make sense of data by predicting trends and relationships that exist with the data.

### Printable Worksheets And Lessons

- Cost and Number of Sales
Step-by-Step Lesson- The outcome of this defies logic, but then
again data has been known to do that at times.

- Guided Lesson - Find
the relationships displayed between : The amount of cheese on pizzas
and price, the salary of employees and the amount they spend, and
tax increases and inflation.

- Guided Lesson Explanation
- This is where students start to finally realize that math has
a real purpose in life.

- Independent Practice -
A nice obstacle course of problems that are spread over three pages.

- Matching Worksheet
- Match the graph to the data tables that they illustrate.

- Scatter Plots and Line of Best Fit Five Pack - This is one of my most used five packs on the site.

#### Homework Sheets

Creating graphs is one of the best ways to see relationships within data sets.

- Homework 1 - So, this graph indicates a steadily falling line of best fit. This indicates a negative relationship between price of items and number of items sold.
- Homework 2 - This indicates a positive relationship between the tax and deflation. As the tax rate decreases, deflation percentage increases.
- Homework 3 - This indicates a negative relationship between the temperature and latitude because as the latitude increases, the average temperature decreases.

#### Practice Worksheets

We give you sets of data and ask you to identify the relationship, if one exists at all.

- Practice 1 - Is there any relationship between the average hours of studying and scores on exams?
- Practice 2 - Is there any relationship between the sale of locks and the sale of keys?
- Practice 3 - Is there any relationship between the number of wall clocks and wrist watches a brand makes?

#### Math Skill Quizzes

These are the most common types of questions that you will see for this content.