Data and Statistics
Chapter 1
BA 201 – Fall 2010
Slide 1
Statistics

Numerical facts such as averages, medians, percents,
and index numbers.

Art and science of collecting, analyzing, presenting,
and interpreting data.
Slide 2
Data and Data Sets

Data are the facts and figures collected, analyzed,
and summarized for presentation and interpretation.

The data set is all the data collected in a particular
study.
Slide 3
Elements, Variables, and Observations

Elements are the entities on which data are collected.

A variable is a characteristic of interest for the
elements.

An observation is the set of measurements obtained
for a particular element.
Slide 4
Data Sets, Elements, Variables, and
Observations
Variables
Elements
Dataram
EnergySouth
Keystone
LandCare
Psychemedics
Stock
Exchange
NQ
N
N
NQ
N
Annual
Earn/
Sales($M) Share($)
73.10
74.00
365.70
111.40
17.60
0.86
1.67
0.86
0.33
0.13
Data Set
Slide 5
Scales of Measurement
Nominal
Ordinal
Interval
Ratio
Slide 6
Scales of Measurement

Nominal – labels or names.
• E.g., CoB, CoST, CoAL, CoH; male or female;
department 1, 2, 3, 4, …

Ordinal - have the properties of nominal data and
the order or rank of the data is meaningful.
• E.g., Freshman, Sophomore, Junior, or Senior
Slide 7
Scales of Measurement

Interval – have the properties of ordinal data, and
the interval between observations is expressed in
terms of a fixed unit of measure.
• E.g., ACT score of 23, 24, 25, …; years.
• Numeric

Ratio - have all the properties of interval data and the
ratio of two values is meaningful.
• E.g., 30 credit hours versus 120 credit hours
• Must include zero
Slide 8
What You Can Do With Scales
Compute
Frequency
distribution.
Median and
percentiles.
Add or subtract.
Mean, standard
deviation, standard
error of the mean.
Ratio or coefficient of
variation.
Nominal Ordinal
Interval
Ratio
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
No
Yes
Yes
No
No
Yes
Yes
No
No
No
Yes
http://www.graphpad.com/faq/viewfaq.cfm?faq=1089
Slide 9
Categorical or Quantitative Data
Categorical (or Qualitative)
 Grouped by categories
 Numeric or non-numeric
 Nominal or ordinal
Quantitative
 How much or how many
 Numeric
 Interval or ratio
 More statistical tests
available
Slide 10
Scales of Measurement
Data
Categorical
Numeric
Nominal
Ordinal
Quantitative
Non-numeric
Nominal
Ordinal
Numeric
Interval
Ratio
Slide 11
Cross-Sectional or Time Series Data

Cross-sectional data are collected at the same or
approximately the same point in time.
• E.g., Building permits in January

Time series data are collected over several time
periods.
• E.g., Building permits each month
Slide 12
Data Sources

Existing Sources – data already exists.

Statistical Studies – data obtained through a study.
• Experimental Studies – variable of interest
identified and other variables controlled.
• Observational studies – no attempt is made to
control or influence the variables of interest.
Slide 13
Descriptive Statistics

Data summarized and presented in a form that is
easy for the reader to understand.

Tabular, graphical, or numerical.
Average
Tune-up
= $79
Slide 14
Statistical Inference

Use data from a sample to make estimates or test
hypotheses about a population.
Slide 15
Statistical Inference

Population – set of all elements in a particular study.
• Census – collects data about entire population.

Sample – a subset of the population.
• Sample survey – collects data for a sample.
Slide 16
Statistical Inference
Population
Sample
Statistics about the sample
provide an estimate of the
population.
Statistics about sample
Slide 17
Slide 18