Chapter 1.1

Descriptive and Inferential Statistics
You’re already familiar with statistics through radio,
television, newspapers, and magazines:
 Eating 10 g of fiber a day reduces the risk of hearth
attack by 14% (Readers Digest)
 In 2008, the average credit card debt for college
students was $3173 (
 About 15% of men in the U.S. are left-handed and 9%
of women are left-handed (Scipps Survey Research
Where is Statistics used?
 Sports
 Health
 Education
 Marketing
 Politics
What is Statistics?
Statistics is the science of conducting studies to collect,
organize, summarize, analyze, and draw conclusions
from data.
Statistics is used to analyze the results of surveys and as
a tool in scientific research to make decisions based on
controlled experiments.
Other uses of statistics include operations research,
quality control, estimation, and prediction.
Why study Statistics?
1. To be able to read and understand the various
statistical studies performed in your field.
2. To conduct research, design experiments, make
predictions, and communicate results
3. Be a more well informed consumer and citizens
1. Variable – a characteristic or attribute that can
assume different values
2. Data – the values (measurements or observations)
that the variables can assume
3. Random variables – variables whose values are
determined by chance
4. Data Set – a collection of data
5. Data value – each value in the data set
Descriptive Statistics
 Descriptive statistics consists of the collection,
organization, summarization, and presentation of
data. It describes a situation.
 Example: US Census
Inferential Statistics
 Inferential statistics consists of generalizing from
samples to populations, performing estimations and
hypothesis tests, determining relationships among
variables and making predictions. It uses probability
(the chance of an event occurring)
 Example: BINGO
Population vs. Sample
 A population consists of all subjects (human or
otherwise) that are being studied. Most of the time, it
is not possible to use the entire population for a
statistical study.
 A sample is a group of subjects selected from a
population. If subjects of a sample are properly
selected, they should possess similar characteristics
as the subjects of the population.
Hypothesis Testing
 A decision-making process for evaluating claims
about a population based on information obtained
from samples.
 An area of inferential statistics
Try it!
 Pg. 5-6 #1-6