Scatter Plots and Predictions

Scatter Plots and Predictions

NC Standards

NC.8.SP.1: Construct and interpret scatter plots for bivariate measurement data to: 

• investigate patterns of association between two quantities. 

• investigate and describe patterns such as clustering, outliers, positive or negative association, linear association, and nonlinear association.

NC.8.SP.2: Model the relationship between bivariate quantitative data to:

• Informally fit a straight line for a scatter plot that suggests a linear association.

• Informally assess the model fit by judging the closeness of the data points to the line.

NC.8.SP.3: Use the equation of a linear model to solve problems in the context of bivariate quantitative data, interpreting the slope and -intercept.

Essential Questions

• How can you construct and interpret a scatter plot?

• How can you describe the data set on a plot?

• How can you represent data that is correlated with a straight line?

Trend Lines

• When scatter plots demonstrate a strong relationship, a straight can be used to show the general pattern of data.

• A trend line, or "line of best fit," is a straight line that should lie as close as possible to the middle of the data in the scatter plot.

For 1-4, write "yes" or "no" to describe whether the trend line is a good fit.

You Try

Multiple Choice

Is this trend line a good fit?

• yes

• no

Multiple Choice

Is this trend line a good fit?

• yes

• no

Multiple Choice

Is this trend line a good fit?

• yes

• no

Multiple Choice

Is this trend line a good fit?

• yes

• no

a. Describe the association of the data.

b. Sketch a trend line on the graph

c. Myla wants to predict the value of y when x = 10. How might the trend line you drew be helpful?

Use the data shown to answer a-c

Multiple Choice

Describe the association of the data.

• positive linear

• positive non-linear

• negative linear

• negative non-linear

Draw

Sketch a trend line on the graph

Open Ended

Myla wants to predict the value of y when x = 10. How might the trend line you drew be helpful?

Sketch a trend line on the graph. Then , use the trend line to help make a pattern.

Predict the value of y when x = 7

Sketch a trend line on the graph. Then , use the trend line to help make a pattern.

Predict the value of x when y = 10.

Sketch a trend line on the graph. Then , use the trend line to help make a pattern.

Predict the value of y when x = 30.

Apply the use of trend lines to help you answer each of the following questions.

Open Ended

Predict the age of a polar bear that weighs 50 lbs.

Open Ended

Predict the weight of a 10-month-old polar bear.

Multiple Choice

A polar bear weighs 42 lbs, and Jaime estimates that the bear is between 4-5 months old. Is his estimation reasonable? Why or why not?

• Yes

  (it's on the trend line)

• Yes

  (It's an outlier)

• No

  (it's on the trend line)

• No

  (It's an outlier)

Open Ended

If Gregory has 45% of his popcorn remaining, predict the percentage of the movie he has watched.

Open Ended

Brianna has watched 60% of the movie. Predict the percentage of her popcorn remaining.

Multiple Choice

Erika has watched 20% of the movie, and her brother bets that only 30% of her popcorn is remaining. Is his prediction reasonable? Why or why not?

• Yes

  (it's on the trend line)

• Yes

  (It's an outlier)

• No

  (it's on the trend line)

• No

  (It's an outlier)