DATA ANALYSIS ch.1

Statistics

the science and art of collecting, analyzing, and drawing conclusions from data.

Individual

An object described in a sat of data.

Variable

An attribute that can take different values for different individuals.

Categorical Variable

Assigns labels that place each individual into a particular group.

Quantitive

relating to measuring, or measured by the quantity of something not the quality

Discrete Variable

Takes a fixed set of possible values with gaps between them.

Continuous Variable

Takes any value in an interval on the number line.

Distribution

A variable that tells us what values the variable takes and how often it takes those values.

Frequency Table

Shows the number of individuals having each value.

Relative Frequency Table

Shows the proportion of percent of individuals having each value.

Bar Graph

Shows each category as a bar.

Pie Chart

Shows each category as a slice of “pie”. The areas of the slices are proportional to the category frequencies or relative frequencies.

Two Way Table

A table of counts that summarizes data on the relationship between two categorical variables for some group of individuals.

Marginal Relative Frequency

Gives the percent or proportion of individuals that have a specific value for one categorical variable.

Joint Relative Frequency

Gives the percent or proportion of individuals that have a specific value for one categorical variable and a specific value for another categorical variable.

Conditional Relative Frequency

Gives the percent of individuals that have a specific value for one categorical variable among individuals who share the same value of another categorical variable.

Segmented Bar Graph

Displays the distribution of a categorical variable for each value of another categorical variable.

Mosaic Plot

Displays the distribution of a categorical variable as segments of a rectangle, with area of each segment proportional to the percent of individuals in the corresponding category.

Association

Knowing the value of one variable helps predict the value of another variable. If it doesn’t help find another variable there is no association.

Dot Plot

Shows each data value as a dot above the location on a number line.

Symmetric

If the right side of the graph is approximately the mirror image of the left side of the graph.

Skewed

If one side of the graph is much longer than the other side. The direction is towards the tail.

Stem Plot

Data that is split into two plots, a stem which is all but the final digit and the leaf (the final digit). Ordered lowest to highest in a vertical column.

Histogram

Shows each interval of values as a bar.

Mean

Average of all data values.

Statistic

A number that describes some characteristic of a sample.

Parameter

A number that describes some characteristic of a population.

Resistant

Is not sensitive to extreme values.

Median

The midpoint of a distribution.

Range

The distance between the minimum value and the maximum value.

Standard Deviation

Measures the typical distance of the values in a distribution from the mean.

Variance

The average squared deviation.

Quartiles

Of a distribution divide the ordered data set into four groups (find the median first) Q1- left of the median Q3- right of the median

Interquartile Range IQR

The distance between the first and the third quartiles.

Five Number Summary

If a data point falls more than 1.5 x IQR above the third quartile or below the first quartile.

Box Plot

A visual representation of the five number summary.