# Tutor Service: Statistical Data

If you need help, check out this guide!

## Exploring categorical data

• The language of variation: Variables
• Representing a categorical variable with graphs
• Representing two categorical variables
• Statistics for two categorical variables

## Exploring one-variable quantitative data: Percentiles, z-scores, and the normal distribution

• Percentiles
• Z-scores
• Density curves
• Normal distributions and the empirical rule
• Normal distribution calculations

## Exploring one-variable quantitative data: Displaying and describing

• Representing a quantitative variable with dot plots
• Representing a quantitative variable with histograms and stem plots
• Describing the distribution of a quantitative variable
• Comparing distributions of a quantitative variable

## Exploring two-variable quantitative data

• Representing the relationship between two quantitative variables
• Correlation
• Residuals
• Least-squares regression
• Analyzing departures from linearity

## Exploring one-variable quantitative data: Summary statistics

• Measuring center in quantitative data
• More on mean and median
• Measuring variability in quantitative data
• Effects of linear transformations
• More on standard deviation (optional)
• Graphical representations of summary statistics

## Collecting data

• Introduction to planning a study
• Potential problems with sampling
• Random sampling and data collection
• Introduction to experimental design
• Inference and experiments