Descriptive and Inferential Statistics
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 (Newser.com)
 About 15% of men in the U.S. are left-handed and 9%
of women are left-handed (Scipps Survey Research
Center)
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
Definitions

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