Statistics for Dummies (6 page)
On the accent page of the Sunday paper, you can read about Dr. Ruth's latest research on people's sex lives. She reports that sex doesn't stop at age 60 or even age 70. That's nice to know, but how did she determine this, and to what extent are people having sex at these ages? She doesn't say (maybe some statistics are better left unsaid, huh?). However, Dr. Ruth does recommend that folks in this age group disregard the surveys that report how many times a week, month, or year a couple has sex. In her view, this is just people bragging. She may be right about this. Think about it, if someone conducted a survey by calling people on the phone asking for a few minutes of their time to discuss their sex lives, who is going to be the most likely to want to talk about it? And what are they going to say in response to the question, "How many times a week do you have sex?" Are they going to report something that is the honest truth, or are they going to exaggerate a little? Self-reported surveys can be a real source of bias, and can lead to misleading statistics. So, don't be too hard on Dr. Ruth (who, by the way, is the author of
Sex For Dummies
, 2nd Edition, published by Wiley Publishing, Inc.). How would you recommend she go about finding out more about this very personal subject? Sometimes, research is more difficult than it seems.
Chapter 2
has more examples of how statistics can go wrong, and what to look for.
The weather report provides another mass of statistics, with its forecasts of the next day's high and low temperatures (how do they decide on 16 degrees and not 15 degrees?) and reports of the day's UV factor, pollen count, pollution standard index, and water quality and quantity. (How do they get these numbers, by taking samples? How many samples do they take, and where do they take them?) You can even get a forecast looking ahead 3 days, a week, or even a month or a year! How accurate are weather reports these days? Given the number of times you get rained on when they told you it was going to be sunny, you could say they still have work to do on those forecasts!
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When looking at how numbers are used (and abused) in everyday life, you can't ignore the world of sports betting, a multi-billion-dollar-a-year business that includes the casual bettor as well as the professional gambler and the compulsive gambler. What kinds of topics can you bet on? Pretty much anything that's got two outcomes. The crazy wagers that a person can make in Las Vegas have no limit (no pun intended).
Here is a sampling of some of the burning issues regarding the Super Bowl that one can wager on at a sports book (a betting place) in Las Vegas:
Which team will have the most penalty yards?
Which team will score last in the first half?
Will a 2-point conversion be attempted?
What will happen first, a score or a punt?
What will the total net yards by both teams be (over 675 or under 675)?
Will both teams make a 33-yard or longer field goal?
Hmm. Why not throw in the number of pounds of guacamole consumed by the Super Bowl TV viewers versus the number of blades of grass (or turf) on the field? Gamblers, start counting.
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| REMEMBER | Probability and computer modeling do play an important role in forecasting today's weather, though, and are especially helpful regarding major events such as hurricanes, earthquakes, and volcano eruptions. Of course computers are only as smart as the people who program them, so scientists still have much work to do before tornados can be predicted before they even begin (wouldn't that be great, though?). For more on modeling and statistics, see |
Moving on to the arts section of the newspaper, you see several ads for current movies. Each movie ad contains quotes from certain movie critics, some of which read, "Two thumbs up!", "The supreme adventure of our time", "Absolutely hilarious", or "One of the top ten films of the year!" Do you pay attention to the critics? How do you determine which movies to go to? Experts say that while the popularity of a movie may be affected by the critics' comments (good or bad) in the beginning of a film's run, word of mouth is the most important determinant of how well a film is going to do in the long run.
Studies also show that the more dramatic a movie is, the more popcorn is sold. Yes, the entertainment business even keeps tabs on how much crunching you do at the movies. How do they collect all of this information, and how does it impact the types of movies that are made? This, too, is part of statistics:
designing and carrying out studies to help pinpoint an audience and find out what they like, and then using the information to help guide the making of the product. So the next time someone with a clipboard asks if you have a minute, you may want to stand up and be counted.
Those horoscopes: You read them, but do you believe them? Should you? Can people predict what will happen more often than just by chance? Statisticians have a way of finding out, by using something they call a hypothesis test (see
Chapter 14
). So far they haven't found anyone that is able to read minds, but people still keep trying!
Take a break from the Sunday newspaper, which you read in the comfort of your home, and move on to the daily grind of the workplace. If you're working for an accounting firm, of course numbers are part of your daily life. But what about nurses, portrait studio photographers, store managers, newspaper reporters, office workers, or even construction workers? Do numbers play a role if that's your job? You bet. This section gives you a few examples of how statistics creep into every workplace.
| REMEMBER | You don't have to go very far to see the tracks of statistics and how it weaves its way in and out of your life and your work. The secret is being able to determine what it all means and what you can believe, and to be able to make sound decisions based on the real story behind those numbers so that you can handle and even become accustomed to the statistics of everyday life. |
Sue works as a nurse during the night shift in the labor and delivery unit at a university hospital. She has several patients that she has to take care of in a given evening, and she does her best to accommodate everyone. Her nursing manager has told her that each time she comes on shift she should identify herself to the patient, write her name on the whiteboard in the patient's room, and ask the patient whether she has any questions. Why does she do this? Because after each mother comes home from the hospital, she receives a phone call a few days later asking about the quality of care, what was missed, what the hospital can do to improve its service and quality of care,
and what the hospital staff can do to ensure that the hospital is chosen more often than the other hospitals in town. Quality service is important, and for new moms staying in the hospital, with nurses coming and going every eight hours, knowing the names of their nurses is important, because this helps them get their questions answered in a timely manner. Sue's raises depend on her ability to follow through with the needs of new mothers.
Carol recently started her job as a photographer for a department store portrait studio; one of her strengths is working with babies. Based on the number of photos purchased by customers over the years, this store has found that people will buy more of the posed pictures than the natural-looking ones. As a result, the store managers will encourage their photographers to take posed shots.
A mother comes in with her baby and has a special request, "Could you please not pose my baby too deliberately? I just like his pictures to look natural." What does Carol say? "Can't do that, sorry. My raises are based on my ability to pose a child well." Wow! You can bet that the mother making the request is going to fill out that survey on quality service after this session — and not just to get $2.00 off her next sitting (if she ever comes back to that studio).
Terry is a store manager at a local pizzeria that sells pizza by the slice. He is in charge of determining how many workers to have on staff at a given time, how many pizzas to make ahead of time to accommodate the demand, and how much cheese to order and grate, all with minimal waste of wages and ingredients. It's Friday night at 12 midnight and the place is dead. Terry has five workers left and has 5 pans of pizza he could throw in the oven, making about 40 slices of pizza. Should he send two of his workers home? Should he put more pizza in the oven or hold off? Terry knows what is most likely to happen because the store owner has been tracking the demand for weeks now, and he knows that every Friday night things slow down between 10 and 12, but then the bar crowd starts pouring in around midnight, and the crowd doesn't let up until the doors close at 2:30 in the morning. So Terry keeps the workers on, puts in the pizzas starting at 30 minute intervals from 12:00 on, and is rewarded with a good night money-wise, with satisfied customers and with a happy boss. For more information on how to make good estimates using statistics, see
Chapter 11
.
Take DJ, the administrative assistant for a computer company. How can statistics creep into her office workplace? Easy. Every office is filled with people who want to know answers to questions, and they want someone to "Crunch the numbers" to "Tell me what this means" to "Find out if anyone has any hard data on this" or to simply say, "Does this number make any sense?" They need to know everything from customer satisfaction figures to changes in inventory during the year; from the percentage of time employees spend on e-mail to the cost of supplies for the last three years. Every workplace is filled with statistics, and DJ's marketability and value as an employee could go up if she's the one the head honchos turn to for help. Every office needs a resident statistician — why not let it be you?
Statistics Gone Wrong
The numbers explosion can leave you feeling overwhelmed and confused (but with the help of this book you'll be able to understand many of the statistics you encounter in everyday life)! The purpose of this chapter is to bring another emotion to the surface: skepticism! Not skepticism like, "I can't believe anything anymore", but skepticism like, "Hmm, I wonder where that number came from." "Is this really true?" "I need to find out more information about this study before I believe these results." The media present you with many examples of statistics gone wrong, and after you find out how to spot these problems, you'll be well on your way to becoming more confident about statistics, ready to tackle the numbers explosion!
Statistics end up on your TV and in your newspaper as a result of a process. First, the researchers who study an issue generate results; this group of people is composed of pollsters, doctors, marketing researchers, government researchers, and other scientists. They are considered the
original sources
of the statistical information. After they get their results, these researchers want to tell people about it, so they typically put out either a press release or a journal article. Enter the journalists, who are considered the
media source
of the information. Journalists hunt for interesting press releases, sort through the journals, and basically search for the next headline. When reporters complete their stories, statistics are sent out to the public. This can happen through a variety of media: TV, newspaper, magazines, Web sites, newsletters, and so on. Now the information is ready to be taken in by the
third group, the
consumers
of the information (you!). You and other consumers of information are the ones faced with the task of listening to and reading the information, sorting through it, and making decisions about it. And as you may have guessed, at any stage in the process of doing research, communicating results, or consuming information, errors can take place, either unintentionally or by design.
