The Practice of StatisticsThird Edition

Chapter P:What is Statistics?

Copyright © 2008 by W. H. Freeman & Company

What is Statistics

• The Art and Science of learning from data.

• Data is numbers with a context.

Statistics at a Glance

Part I

•Exploratory Data Analysis (EDA) - Organizing,

describing, and analyzing dataPart II

Producing Data - Surveys, Experiments, and Observational studies

Part IIIProbability

Part IVStatistical Inference

Data Analysis: Organizing, displaying, summarizing data

Meeting a new data set...

Who are the individuals described by the data?

What are the variables? Units?

Why were the data gathered?

When, where, how, and by whom were the data produced?

This is an example of

a Categorical Variable

Describing Quantitative Variables(pg. 16)

Soccer goals scored by the US women's soccer

team in 34 games during the 2004 season.

3 0 2 7 8 2 4 3 5 1 1 4 5 3 1 1 3 3 3 2 1 2 2 2 4 3

5 6 1 5 5 1 5

What do the numbers tell us?

This is a example of a Quantitative Variable.

U.S. Women’s Soccer Team 2004

Where to Get Good Data

• Library

• Internet (Government Agencies, NOT

Wikipedia!!!)

• Good data ALWAYS is better than personal

experience The plural of anecdote

is not data.

The library and Internet are examples.

Sometime You Need to Produce

Your Own Data.

• Surveys

– Getting valid survey results is hard

– Where the data comes from matters.

• Experiments

• Observational Studies

What is an example of an Observational Study?

What is an example of an Experiment?

Are surveys an observational study or experiment?

Probability

• Toss a coin

– What is the probability of a head?

– What is the probability of a tail?

• What does this mean for the next toss of the

coin?

• What is going to happen over the long run?

• If I flip a coin four times, am I guaranteed

to get heads twice?

The big idea of probability:

Chance behavior is unpredictable in the short run but has a predictable pattern in the long run.

Population

Sample

Data/Statistics

Inference/

Conclusions

• Drawing Conclusions from the data

– The largest and most important part of this course.

Inference

• Do high school students cheat on exams?

– An internet survey of 1,200 HS students and

asked: “Have you ever cheated on an exam?”

– 48% answered yes.

What Conclusion Can we Draw?

• If we sampled ALL high school students

would exactly 48% answer “Yes”?

• More likely we can find a range that we can

be very confident that contains true

percentage of all students who would

answer “Yes”.

Statistical Inference

•Even under the best of situations, variation is

everywhere.

•When we study statistical inference, we learn that

even with variation, we can make statements that

we ARE confident in.

Assignment

• Problems P3, P7 – P9, P11

• Watch: https://www.learner.org/courses/againstallodds/unitpages/unit02.html

(11.49 min.)

• Read Pages 38 - 48

Reminder: Chapter P Guide