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