Frequency Tables
Cumulative Frequency Table displays the number of scores, in total, in a class and all
the lower classes
Relative Frequency Table displays the percentage of values that fall in each class
Frequency Distribution Cumulative Frequency
Freque

Bias in Statistics
Gallup predicted Roosevelt's victory.
He showed why the Digest's flawed methods predicted Landon would win.
The Digest folded up: Gallup became America's predictor
After being a hero in 1936
In 1948 Gallup blew the Truman-Dewey predicti

Descriptive Statistics
Frequency Distributions
List categories (classes) and the number of occurrences in each category
o Summarize data by developing categories and consolidating data into categories
o Present an abbreviated form of the data set
o Catego

Box Plot & the Interquartile Range
Interquartile Range [IQR]
The middle 50%
IQR = Q3 - Q1 where
Q3: Upper quartile
Value above which 25% of the observed cases fall and below which 75% of the observed
cases fall
Q2: Median:
50% above / 50% below
Q1: Lower

Example of Sample Statistics
What if the production run consisted of 10000 toys and only 40 were defective?
What if the production run consisted of 10000 toys and only 460 were NOT defective?
A manufacturer of childrens toys claims that less than 5% of hi

Introduction to terms you use in Statistics
Statistics Why?
Why should we care about statistics?
Have you ever watched the weather forecast?
Have you ever read the news and heard reports about the prices of homes sold recently?
Are you a sports fan? Do yo

Nominal Scales
Rule: Partition data into mutually exclusive & collectively exhaustive categories
Different numbers = Different objects or Different numbers = Different category
Ordinal Scale
Numbers are used to order objects according to the amount of som

Median and Mode
o Measures we use to calculate one value that best describes a group of numbers
Median: the point at which an equal number of values fall below and fall abovethe middle
value
Mode: the value with the highest frequency
Can be no mode, one o

A GENERAL RULE for any distribution:
o MOST OF THE TIME 50% or more of the values will lie within 1 Standard Deviation of
the mean
o MOST OF THE TIME 90% or more of the values will lie within two standard deviations
of the mean
o MOST OF THE TIME ALL the

Histogram
Polygon
Polygon
450
Frequency
400
350
300
250
200
Frequency
150
100
50
0
12.5
38.5
64.5
90.5
116.5
142.5
Class
Stem and Leaf Plots - Stem and leaf plots describe data by consolidating; in the example below
the first digit(s) is(are) the stem(s)