Why study statistics?

CHAPTER 1 Exploring Data Introduction Data Analysis: Making Sense of Data

Data Analysis: Making Sense of Data IDENTIFY the individuals and variables in a set of data CLASSIFY variables as categorical or quantitative

Statistics is the science of learning from data. Data are numbers with a context. Data Analysis is the process of organizing, displaying, summarizing, and asking questions about data. Data beat personal experiences Do cell phones cause brain cancer? Where the data comes from matters If you had it to do over again, would you have children? Who talks more – men or women? Always plot your data “You can observe a lot just by watching.” Yogi Berra

Individuals and Variables objects described by a set of data Variable any characteristic of an individual Categorical Variable places an individual into one of several groups or categories. Quantitative Variable takes numerical values for which it makes sense to find an average.

Dotplot of MPG Distribution Data Analysis A variable generally takes on many different values. We are interested in how often a variable takes on each value. Distribution tells us what values a variable takes and how often it takes those values. Dotplot of MPG Distribution Variable of Interest: MPG

How to Explore Data Examine each variable by itself. Then study relationships among the variables. Start with a graph or graphs Add numerical summaries

From Data Analysis to Inference Population Sample Collect data from a representative Sample... Make an Inference about the Population. Perform Data Analysis, keeping probability in mind…

Data Analysis: Making Sense of Data A dataset contains information on individuals. For each individual, data give values for one or more variables. Variables can be categorical or quantitative. The distribution of a variable describes what values it takes and how often it takes them. Inference is the process of making a conclusion about a population based on a sample set of data.

Hiring discrimination: It just won’t fly!

Unfortunately, only eight captain positions are available right now. An airline has just finished training 25 junior pilots – 15 male and 10 female – to become captains. Unfortunately, only eight captain positions are available right now.

announce that they will use a lottery process Airline managers announce that they will use a lottery process to determine which pilots will fill the available positions.

identical slips of paper, The names of all 25 pilots will be written on identical slips of paper, placed in a hat, mixed thoroughly, and drawn out one at a time until all eight captains have been identified.

A day later, managers announce the results of the lottery A day later, managers announce the results of the lottery. Of the 8 captains chosen, 5 are female and only 3 are male.

suspect that the lottery was not carried out fairly. Some of the male pilots who were not selected suspect that the lottery was not carried out fairly.

Could these results have happened just by chance? The key question in this possible discrimination case is: Could these results have happened just by chance? Let’s find out!

Process: 25 possible pilots to choose 8 captains 15 male 10 female

Choose 15 chips of one color to represent males Process: Choose 15 chips of one color to represent males Choose 10 chips of a different color to represent females Mix the chips together in a cup and without looking choose 8 chips. Record the number of chips that represent female. Repeat this procedure 5 times.

In your opinion, was there discrimination in this hiring process? Outcome: In your opinion, was there discrimination in this hiring process?