Ch. 2 : data

Warm-Up Identify the 5 W’s (Who, What, When, Where, and Why) for the following: On April 13, 2016, Kobe Bryant scored 60 points during his last game for the Los Angeles Lakers at the Staples Center.

What are Data? Do data have to be numbers? I.E. amount of your last purchase in dollars How about when data have values that are numerical but serve as labels? Can you think of some examples? Data values are useless without their context!

Five W’s and sometimes How Answering these questions provide the context for data values Who and What are essential for understanding the data

Who? The who of the data are who or what we have collected data on (known as cases) Individuals answering surveys are known as respondents, those we experiment on are called participants, but animals, plants, Web sites are called experimental units Other times, data values are simply known as observations with no clear indication of who

What & Why? The characteristics recorded for each case are called variables (What exactly are we recording?) 3 types: categorical, quantitative, and identifier Categorical variables deal with categories Quantitative variables tend to have measurement units Identifier variables are unique and serve as labels To figure out which kind of variables you have, you must figure out why the data was collected

Practice In a study appearing in the journal Fashion, a research team reports that today’s high schoolers are spending more money on shoes than previous generations. Records of high schoolers born in the late 90’s to early 2000’s indicate that money spent on shoes is on average, $600 per year.

A study of state-sponsored Lotto games in the United States listed the names of the states and whether or not the state had Lotto. For the states that did, the study indicated the number of numbers in the lottery, the number of matches required to win, and the probability of holding a winning ticket.

A Tricky Example Imagine Amazon asking for your age in years Is this variable quantitative or categorical?

Cont. The answer is it depends! If they wanted to know the average age of customers who visit their site after 3 a.m. then the variable would be quantitative. On the other hand, if they wanted to know which T.V. show to offer you (for Prime accounts only), knowing if you are a child, teen, adult, or senior, then age would be categorical.