Chapter 3: Describing Data Visually

Variability (3 questions)

1. How much dispersion is there in the data? 2. How spread out are the data values? 3. Are there unusual values?

Measurement (4 questions)

1. What are the units of measurement? 2. Are the data integers or continuous? 3. Any missing observations? 4. Any concerns with accuracy or sampling methods?

Center (2 questiosn)

1. Where are the data values centered? 2. What seem to be typically?

Visual

Done in charts or graphs

Numerical

Done in statistics or tables

Skewness

Shows a histograms skewness. indicated by the direction of its longer tail

Sturges' Rule

Shows how to choose the number of bins for a frequency distribution 1 + 3.3 times Log(# of observations)

Scatter plots

Shows n pairs of observations as dots on an X-Y graph. investigated the relationships between two variables & to see of there's an association

Shape

Symmetrical, skewed, sharply peaked, flat, bi-modal

Cumulative frequency

The 2nd type of frequency distribution. accumulate as the bin limit increase

Left negatively skewed

histogram has a longer left tail, with most data values clustered on the right side

Right positively skewed

histogram has a longer right tail, with most data values clustered on the left side

Symmetric

if neither tail of the histogram is either

Histogram

is a graphical representation of a frequency distribution

Modal Class (for shape)

is a histogram bar that is higher than those on either side

Bar chart

is a horizontal display of data. Includes percent and categorical variables

Column chart

is a vertical display of data. Includes percent and categorical variables .

Outlier

is an extreme value that is far enough from the majority of the data that it probably arose from a difference to cause or is due to measurement error

Line chart

is used to display a time series, to spot trends, or to compute time periods

Stacked column charts

the bar height is the sum of several sub totals

Data tables

the simplest for of data display. Done by arranging numbers in rows and columns.

Data can be in 2 types

visually or numerically

Relative frequency

One type of frequency distribution frequency for a bin / the total number of data values (n)

Pareto Chart

a bar graph whose bars are drawn in decreasing order of frequency or relative frequency

Uni-modal

a histogram with a single modal class

Multimodal

a histogram with mire than to modal classes

Bi-modal

a histogram with two modal classes