Such Material! So Content!

Class Discussion Time Why do we discuss a “statistic” but we do not discuss a “mathematic” or a “physic”? A gentle warning: if we do not have a productive student-lead discussion, I will instead turn this into an individual writing prompt. Timed, of course.

Think, Show, and Tell Think Show Tell Before we can solve the problem, we will need to spend serious time considering it seriously. Show An answer without a method or without evidence is at best an opinion, at worst a lie. Tell Even people who have taken Statistics need answers to be broken down. (Let alone those who have not!)

Types of Summaries of Data Visual Commonly used in Think and Show Numerical Commonly used in Show Verbal Commonly used in Think and Tell Any complete analysis of data almost always includes all three of these.

More About Data Numerical data (quantitative) Usually counts of things Names or labels (categorical/qualitative) The Five W’s Who What When Where Why How

Context Without context, data is just stuff. If you can’t answer the who and the what you don’t have data. And you don’t have any useful information.

Two Houses, Both Alike In Dignity Categorical Variables are variables which have data that are names, labels, or indicators. These can be numbers, such as a social security number or zip code, or in some situations…age. Quantitative Variables are variables which have data that are counts or measurements within a category. These will be numbers, although not all numbers are this kind of variable. There will be units of measurement.

Categorical vs Quantitative You measure how many subjects fit a particular label. The whos (subjects) are simply tallied into their whats (the labels) Ex. If we sorted people into categories of tall, medium, and short Each subject is measured with regard to the variable. This measurement will have units of measurement, although they might be trivial. Ex. If we recorded everyone’s actual height

Categorical or Quantitative? Gender Age 17, 21, 44, 76

Univariate or Bivariate Univariate data has only one variable. Bivariate data has two variables. Multivariate data has more than one variable. In this class, we do certain specific things with bivariate data, and then most of what we do will be done with univariate data.

Question Words on Parade The Who, What, When, Where, Why, and How are all very important in Statistics. You need the Who and the What just to have data. You need the Why or else the data is not meaningful. The When and the Where help you to determine if the data can be applied another way. The How lets you know if analyzing the data is meaningful and worthwhile by determining if the method of gathering data was reliable.

Who - Subjects Answers the question, “About whom (or what) has data been collected?” The who can be referred to as Respondents Subjects Participants Experimental units Records Cases p. 9

Who “Who is the data being collected about?” Sometimes the who is not people, but instead something else. So a more universal question is “Who/What is the data being collected about?” While it could be important…this question is not the same as asking who did the collecting. It could, however, be very important to know who collected the data.

What - Variables Characteristics about each individual whose value varies from case to case. Categorical (qualitative) – the variable names categories or answers questions about how cases fall into those categories. Quantitative – a variable measured in units or answers questions about the quantity of what is measured, how many or how much.

What “What data was actually collected?” More than one variable might have been collected. The collected variables will, in the context of the study, be either categorical or quantitative, but never both. A study may, however, have both categorical and quantitative variables. Each one of those variables, however, will be one kind or the other.

When/Where While not as necessary as the Who or What, this information is still context. How many studies from before there were internet or cell phones are still valid today? Is a study done in California valid in Alaska? Would knowing about the job market in Idaho Falls tell you about the job market in Pocatello?

Why “Why was the data collected?” Someone took time to get this data. This is the presumable motivation for gathering it. Even if it is not stated, it can sometimes be very obvious. The Neilson Company estimates ratings for television shows. Why? All about the Benjamins!

How “How was the data collected, and were the methods reliable?” For now you can only take your best intuitive guess at this. There is an entire unit on how to gather data reliably. It is Unit 3. We are in Unit 1. So you are not ready to be all fancy about it yet, and I get that. Do your best.

The Five W’s A Consumer Reports article on energy bars gave the brand name, flavor, price, number of calories, and grams of protein and fat.

Problem #2 Who? Who: The 30 other companies What? Not Fortune Magazine and not the company doing the study. What? What: 401(k) participation rates When? When: Not given 1992 is simply when the article was published.

Problem #2 Where? Where: Not given Why? Why: To see if the company’s participation in 401(k) was low compared to other companies. How? How: The 30 companies were asked what their participation rates are. After we do unit 3, you would have a more detailed answer, such as commenting on the sampling procedure used.

Problem #2 For each variable (“What” Answer), we need to identify if it is categorical, or quantitative. The variable, 401(k) participation rates, is likely being used as a quantitative variable. The participation rate does not have specified units, although the units are most likely percentage of the total employees. Even though the instructions for doing this occur after the instructions to identify the question words, you can totally do this while you are doing the “what”. It is more efficient, in fact.

Problem #2, Final Output Who: The 30 other companies What: 401(k) participation rates (Quantitative; Units: % of total employees) When: Not given Where: Not given Why: To see if the company’s participation in 401(k) was low compared to other companies. How: The 30 companies were asked what their participation rates are.

Assignments: Finish Reading Chapters 1 and 2 if you have not already. Chapter 2 exercises: 2-7, 25, 26 Due Friday You can turn them in sooner, either physically or via e-mail, and that is fine with me. There will be a chapters 1-3 Quiz on Friday We just finished discussing chapter 2, so a good student would know what that means in terms of the reading. I’ll cut you some slack…you only need to read chapter 3 thru the top part of page 31 for tomorrow. Read the rest for Thursday.

Quiz Bulletpoints Know what T-S-T stands for and what each one means. Know how to identify the 5 W’s and How in a study. Know the difference between a qualitative and quantitative variable. Know how to find percentages from a contingency table. Know the area principle.