Internet use and life expectancy. The following scatterplot...

Internet use and life expectancy. The following scatterplot was created as part of a study evaluating the relationship between estimated life expectancy at birth (as of 2014) and percentage of internet users (as of 2009 ) in 208 countries for which such data were available. ${ }^{23}$ (a) Describe the relationship between life expectancy and percentage of internet users. (b) What type of study is this? (c) State a possible confounding variable that might explain this relationship and describe its potential effect.

Internet use and life expectancy. The following scatterplot was created as part of a study evaluating the relationship between estimated life expectancy at birth (as of 2014) and percentage of internet users (as of 2009 ) in 208 countries for which such data were available. ${ }^{23}$
(a) Describe the relationship between life expectancy and percentage of internet users.
(b) What type of study is this?
(c) State a possible confounding variable that might explain this relationship and describe its potential effect.

Key Concepts

Scatterplot Analysis

A scatterplot is a graphical display used to show the relationship between two quantitative variables. The arrangement of points helps identify correlations, trends, and potential patterns in the data. This concept is central for visually evaluating whether increases in one variable tend to be associated with increases or decreases in the other.

Observational Studies

Observational studies involve collecting data without any intervention or manipulation by the researcher. Such studies observe associations in naturally occurring settings, but they cannot definitively establish cause-and-effect relationships due to potential biases and the presence of confounding factors.

Ecological Study Design

Ecological studies analyze data at the group or population level rather than at the individual level. They are useful for identifying trends or associations across regions, countries, or other collectives, but they have limitations such as the ecological fallacy, where relationships observed at the group level may not apply to individuals.

Confounding Variables

A confounding variable is an extraneous factor that relates to both the independent and dependent variables, potentially distorting the true relationship between them. Identifying and accounting for confounders is crucial in observational studies to avoid misleading interpretations of correlations as causal effects.

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