# Scatter plots

**Scatter plots are **visualizations of two variables like X and Y. They are a fundamental tool in statistial disciplines as the regression analysis. Scatter plots help visualizing the relationship between X and Y which is the main objective in regression analysis.

## Scatter plots example

Say we wish to visualize the relation between property prices and year. Let’s take the period of the financial crisis starting in 2008. X is the **independent variable** (year) and Y the **dependent variable** (price):

**The regression analysis** is a so-called **bivariate analysis** because it has two variables (X and Y). Through the regression analysis we can explore the correlation between Y is of X. In our example, we discover how dependent the property prices are based on the variation in year.

The scatter plot graph can answer to questions like these:

**how much does price**(Y) vary from year 2008 to 2010 (X)?**Is there correlation**between the property prices (Y) and year (X)?- How does property
**price (Y) change as year (X) changes**?

## Types of correlation

While scatter plots expose the association between the X and Y, **they do not describe the relation in cause and effect**. Example of different types of correlation between X and Y:

## Direction, strength and linearity

Let’s hand draw an approximated trendline or a regression line and qualify this line as to its direction, strength and linearity which are terms often applied in statistical analysis:

In regression line and in most of the chapters related to regression analysis, we go apply the scatter plots for varies different purposes.

## Learning statistics

- Khan Academy (video 8:12): The video that I’ve based this page on: Bivariate relationship, linearity, strength and direction
- Mathsisfun (text page): Scatter plots

#### Carsten Grube

Freelance Data Analyst

##### Two-sample inference

##### Normal distribution

##### Confidence intervals

##### Simple linear regression, fundamentals

##### ANOVA & the F-distribution

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