Chapter 4. Models are the Building Blocksof Science
You know what a model airplane is. But models are ubiquitous. Advertisersmanipulate you with models, and models determine your success in business orschool. Because the scientific method is a way to think about models, if youare to understand the scientific method, you must be able to recognize modelswhen you see them and appreciate their limitations.
Models as Building Blocks and Substitutes
The model is the most basic element of the scientific method. Everythingdone in science is done with models. A model is any simplification, substituteor stand-in for what you are actually studying or trying to predict. Models areused because they are convenient substitutes, the way that a recipe is aconvenient aid in cooking. This section of the book is dedicated to explainingwhat models are and how they are used.
Models are very common. The ingredients list on a bottle of ketchup is amodel of its contents, and margarine is a model of butter. A box score from abaseball game is a model of the actual event. A trial over an automobileaccident is a model of the actual accident. A history exam is a model designedto test your knowledge of history.
A model is a substitute, but it is also similar to what it represents. Thusthe ingredients list is a fairly accurate guide to the contents of the ketchupbottle. Margarine looks and spreads like butter, and can substitute for it inmany recipes. The box score contains most of the critical information about thebaseball game---such as the winner, the final score, and the pitchers.Similarly, trials and history exams contain the essence of the events theymodel. In fact, models are more than just common, they are ubiquitous. Nearlyeverything we encounter is a model. To drive home this point, we list in Table4.1 several objects or ideas that are models.
Table 4.1 Everyday Models
| Model | What the model represents |
| Cake recipe | Process of making a cake |
| Wedding pictures | The wedding |
| Chapter title | Chapter contents |
| News article about Chicago Cubs' latest loss | The game itself |
| Home video of police arresting a motorist | Police conduct in general |
| Road map of Madison, Wisconsin | Paths of transit in Madison |
| Household budget | Household expenses and income |
| Political candidate's campaign promises | Candidate's performance if elected |
| a statistical average | something close to what can be expected |
Models inside science
Scientific models are fundamentally the same as models outside of science,which will be introduced below. Many people think mistakenly that scientificmodels are always complicated, impenetrable mathematical equations. But intruth, many scientific models are just as understandable as are models foundoutside of science.
The USDA food pyramid, which recommends the proportions of different kindsof foods in a healthy diet, is a model of the thousands of scientific studiesthat have been undertaken on the relation among cancer, heart disease and diet.The figure summarizes these studies in a picture that recommends healthy diets.Thus, this figure is a substitute for the many scientific studies on diet, andit is also a substitute for an actual diet.
As a second example, when scientists use rats to determine whether a foodadditive causes cancer, the rats become a model of humans. Rats are convenientbecause they are relatively easy to raise in the lab (at least compared tohumans), and one can perform experiments on them relatively quickly (in amatter of months rather than years). Moreover, most people find it more ethicalto experiment on rats rather than humans.
Hypotheses and Theories as Models.
We've all heard about hypotheses and theories, especially inphysics and chemistry. Theories usually comprise some idea that scientists haveabout how nature works, but that they aren't totally sure. Hypotheses and theoriesare merely particular kinds of models that we will refer to below as abstractmodels.
Big Models and Small Models.
Even the most rudimentary science course contains some ofthe grand, all-encompassing, models that scientists have discovered. The periodictable of the elements is a model chemists use for predicting properties of theelements. Physicists use Newton's law to predict how objects will interact,such as planets and spaceships. In geology, the continental drift modelpredicts the past positions of continents. But these three models are atypicalbecause they are immensely successful. Most models used are nowhere near sopowerful or widely useful. But scientists use these less-successful onesanyway. Models are used at every turn in a scientific study. Samples aremodels. Ideas are models. Methods are models. Every attempt at a scientificstudy involves countless models, many of them small and of interest only to asmall group of other scientists. The primary activity of the hundreds of thousandsof U.S. scientists is to produce new models, resulting in tens of thousands ofscientific papers published per year.
Models outside science
Trying to enumerate all the models found in business, industry, and society issimply impossible. Models pervade all white collar jobs. Table 4.2 shows modelsfrom fields as diverse as advertising, architecture, finance and manufacturing.In this table we have chosen to give a single model from each of a number offields. However, we could have just as easily picked one job, say retail sales,and listed 150 models associated with it.
Table 4.2 Models in Business and Government
| Field | Common type of model |
| Advertising | Response to an advertisem*nt tested in a single city is a model of the national response to the ad. |
| Architecture | The plans for a new building are a model of the actual building. |
| Business | Past dealings with a client are a model of the trustworthiness and promptness you can expect from her/him in the next deal. |
| Education | A student's performance on a history exam is a model of everything learned about history since the last exam. |
| Finance | The rating Morningstar gives a bond fund is a model of the fund's future performance. |
| Federal gov't | The federal budget is based on an economic model that predicts next year's revenues and expenditures. |
| Franchising | A company uses its existing stores to model the likely success of stores it is considering building. |
| Law | A criminal trial provides a model of the actual crime. |
| Manufacturing | Profit projections are based on a model of material and labor costs as well as sales price. |
| Medicine | Your doctor's diagnosis of the cause of your back pain is a model of its actual cause. |
| Prisons | A model, based on age, crime, and family status, is used to predict which prisoners are good candidates for parole. |
| Retail Sales | The December sales in 1995-2003 model the December sales expected in the coming year. |
The ability to recognize, construct, and improve models gives you anadvantage in many walks of life. A salesperson who recognizes that a salespitch is a model can take steps to improve it. Other models are obvious but areso complicated that years of effort go into learning how to build them, as withthe house, computer, and automobile models that are the trade of architects andengineers. Sometimes, the critical skill is not finding or building a model,but knowing how to improve an existing model, as with a budget or airlinedesign.
Models are important outside of science because success in any professionalendeavor involves accurately predicting or manipulating the future, and we needmodels to do this. Correctly predicting the stock market would net a personfame and fortune. The path to success in sales is only slightly less direct. Ifa salesperson can accurately predict how a particular client will respond to aparticular pitch, the pitch can be modified to have maximum effectiveness,thereby increasing the probability of a sale or abandoning a non-buyer beforewasting much time. Similarly, budgets predict the financial consequences oftaking various actions, allowing the company to cut losses and increaseprofits.
The arts---whether an action movie like Lethal Weapon III, an abstractpainting by Picasso, a historical novel by Michener, or Whitman'spoetry---consist of models designed to evoke emotions and present unusualevents or viewpoints. Because a scene from a Hollywood movie appears to be aplausible representation of the real world, it can make you frightened (a stuntman hanging out the window), or sad (a dead heroine), or anxious (an oncoming train).The protagonist of a historical novel substitutes for someone that actuallylived.
Models exhibit a one-to-many andmany-to-one relationship
There is no such thing as just one model of something, nor is anything we useas a model necessarily useful as just one kind of model. A wedding will havemany different models to remind us of the day: pictures, memories, weddingpresents, and newspaper accounts -- all models of one event. At the same time,one of those wedding presents (e.g., a toaster) will be a model of the weddingbut is also a model of other toasters, of the company that made the toaster(and its other products), and it may eventually become a model of electronicappliances when one of the kids (or parents) takes it apart to fix it or seehow it works.
It is neither profound nor particularly useful to learn that everything is amodel. If this was all we could say about models, there would be no call tofocus heavily on them. The models we have discussed thus far were chosen toshow that you are already familiar with models. In the remainder of thischapter, we describe models that are more subtle, and we explain how anunderstanding of models may be important to people outside of science.
Classes of Models
Different kinds of models are used for different purposes. Table 4.3 liststhree major types that will be used in this class: abstract, physical, andsampling models. Not all models fit neatly into these categories. Moreover, wewon't bother to classify many of the models in this course. However, thesethree classes do accommodate many of models that we will focus on and discuss,so it is convenient to group them in this fashion.
Table 4.3. Classes of models
| Class | Familiar types | Examples & comments |
| Abstract | predictions, theories, hypotheses, many mathematical and computer models | Newton's laws in physics, plans, recipes, statements such as "taking anabolic steroids increases one's strength," or "smoking causes lung cancer." |
| Physical | organisms and their properties, replicas, structures, demonstrations | a globe is a physical model of the earth, each of us is a model for other humans, and the physical structures used in chemistry class are models of molecules |
| Sampling | random choice, personal preference | the sampling model refers to the way that subjects are chosen for a study and divided up among the different groups; sampling models are the subject of our section on Data. |
Summary
You should end this chapter with an understanding that models are a crucialelement of the scientific method. A model is in some way a substitute for whatis being studied. They are widely used, and there are many types of them. Atthis point in the book, you should be able to begin using the information beingtaught. For example, when reading news articles on topics relevant toscientific study, you should be able to identify models used in those studiesand should be able to identify those belonging to the classes in Table 4.3.
Table of contents
Copyright 1996-2000 Craig M. Pease & James J. Bull
