Line Graphs & Scatterplots

Line graph

A figure that is developed by joining a series of plotted points with a line to illustrate how a variable changes over time

X-axis (horizontal)

documents time

Y-axis (vertical)

documents the mean score of a variable

How can line graphs be used in studies?

They can compare the values of 3 or 4 variables or identify changes in a selected variable over time.

What is the purpose of a line graph?

Line graph illustrates the results from descriptive data analyses and identifies patterns in data over time

What types of relationships can be identified in line graphs and scatterplots?

Relationships such as trends, correlations, and changes over time.

What is a scatterplot?

A scatterplot describes relationships between two variables and provides a graphic representation.

How is each point on a scatterplot represented?

Each point represents a subject's scores for variables x and y, illustrating the relationship between the two variables.

What does the display of points on a scatterplot indicate?

The direction (positive or negative) and strength (weak, moderate, or strong) of the relationship between the two variables.

What does a scatterplot with points moving from the lower left to the upper right indicate?

A positive or direct relationship between the two variables.

What does a scatterplot with points moving from the upper left to the lower right indicate?

A negative or inverse relationship between the two variables.

What is the range of strength for relationships shown in a scatterplot?

Strength ranges from -1 to +1, with -1 indicating a perfect negative relationship and +1 indicating a perfect positive relationship.

What does Pearson r measure in the context of scatterplots?

It determines the strength of the relationship between two variables.

How is a weak relationship defined in terms of Pearson r?

A weak relationship is indicated by values less than 0.30 or greater than -0.30.

How is a moderate relationship defined in terms of Pearson r?

A moderate relationship is indicated by values between 0.30 to 0.50 or -0.30 to -0.50.

How is a strong relationship defined in terms of Pearson r?

A strong relationship is indicated by values greater than 0.50 or less than -0.50.

What does it indicate if plotted points are closer together on a scatterplot?

It indicates a stronger linear relationship between the two variables.

What does it indicate if plotted points are widespread across the graph?

It indicates a weak relationship that is closer to 0.

What are outliers in a data set?

Extreme values that occur due to inherent variability, measurement error, sampling error, or errors in study implementation.

How do outliers affect a data set?

They can skew the data set or affect the normality of the frequency distribution, serving as exceptions to the overall findings.

Why might researchers include a scatterplot in their study publication?

To identify linear and nonlinear relationships.

What elements are included in a scatterplot?

An x-axis with one variable's name, a y-axis with another variable's name, and points representing study participants' scores.