Abstract
Although some of us may not like to admit it, everyone's afraid of something. Big dogs, thunderstorms, public speaking, heights: what are you most afraid of? Do you think grown-ups have the same fears as kids? How about first-graders and sixth-graders? Find out for yourself by doing this project.Summary
Andrew Olson, Ph.D., Science Buddies
Objective
The goal of this project is to measure whether common fears change with age, and, if so, how.
Introduction
To do this study, you will first need to write and then to administer a survey about common fears. What kinds of things are people afraid of? Do the things people are commonly afraid of change with age?
The Experimental Procedure section has some suggestions on survey design. You can also find information on the Science Buddies Sociology Resource page, Designing a Question-Based Study.
In order to have confidence that your survey results are representative, it is critically important that you have a large number of randomly-selected participants in each group you survey. So what exactly is "a large number?" For a 95% confidence level (which means that there is only a 5% chance of your sample results differing from the true population average), a good estimate of the margin or error (or confidence interval) is given by 1/√N, where N is the number of participants (Niles, 2006). The table shows this estimate of the margin of error for sample sizes ranging from 10 to 10,000. (For more advanced students with an interest in statistics, the Creative Research Systems website (Creative Research Systems, 2003) has a more exact formula, along with a sample size calculator that you can use. For most purposes, though, the 1/√N approach is sufficient.)
| sample size (N) |
margin of error (fraction) |
margin of error (percentage) |
| 10 | 0.316 | 31.6 |
| 20 | 0.224 | 22.4 |
| 50 | 0.141 | 14.1 |
| 100 | 0.100 | 10.0 |
| 200 | 0.071 | 7.1 |
| 500 | 0.045 | 4.5 |
| 1000 | 0.032 | 3.2 |
| 2000 | 0.022 | 2.2 |
| 5000 | 0.014 | 1.4 |
| 10000 | 0.010 | 1.0 |
You can quickly see from the table that results from a survey with only 10 random participants are not reliable. The margin of error in this case is roughly 32%. This means that if you found, for example, that 6 out of your 10 participants (60%) had a fear of heights, then the actual proportion of the population with a fear of heights could vary by ±32%. In other words, the actual proportion could be as low as 28% (60 − 32) and as high as 92% (60 + 32). With a range that large, your small survey isn't saying much.
If you increase the sample size to 100 people, your margin of error falls to 10%. Now if 60% of the participants reported a fear of heights, there would be a 95% probability that between 50 and 70% of the total population have a fear of heights. Now you're getting somewhere. If you want to narrow the margin of error to ±5%, you have to survey 500 randomly-selected participants. The bottom line is, you need to survey a lot of people before you can start having any confidence in your results.
Terms and Concepts
To do this project, you should do research that enables you to understand the following terms and concepts:
- sample size,
- population,
- confidence level,
- margin of error (confidence interval).
More advanced students will also want to study:
- statistical significance,
- null hypothesis.
Questions
- How many people would you have to survey in order to have a 2.5% (i.e., 0.025) margin of error?
Bibliography
- This webpage calculates the sample size required for a desired confidence interval, or the confidence interval for a given sample size:
Creative Research Systems, 2003. Sample Size Calculator,. Retrieved June 28, 2006. - This website has information on statistics and statistical tests, written for the non-mathematician:
Niles, Robert, 2006. Robert Niles' Journalism Help: Statistics Every Writer Should Know, RobertNiles.com. Retrieved June 28, 2006. - Here is an Excel tutorial to get you started using a spreadsheet program:
Excel Easy. (n.d.). Excel Easy: #1 Excel tutorial on the net. Retrieved July 15, 2014.
Materials and Equipment
To do this experiment you will need the following materials and equipment:
- surveys,
- volunteers of different age groups,
- computer with spreadsheet software (e.g., Excel or QuattroPro) for analyzing and graphing results.
Experimental Procedure
Note: There are special considerations when designing an experiment involving human subjects. ISEF-affiliated fairs often require an Informed Consent Form for every participant who is questioned or observed. In all cases, the experimental design must be approved by a scientific review committee (SRC) prior to the commencement of experiments or surveys. Please refer to the ISEF rules for additional important requirements for studies involving human subjects: http://www.sciserv.org/isef/document.
Designing and Administering the Survey
- You will need to decide which age groups you want to survey. You might be interested in comparing elementary school and middle school students, for example, or teenagers and adults. Make sure that you can find enough participants (100 is a bare minimum) for each age group so that your results are meaningful (see Introduction).
- The survey should be anonymous. You will want to ask the age of each participant, and perhaps also the gender (see Variation #2).
- You will need to think of questions to ask in your survey. The Science Buddies Sociology Resource page, Designing a Question-Based Study, has a lot of useful information. Here are some suggestions to think about when writing your survey:
- You can use structured questions, open-ended questions, or both. An example of a structured question would be:
Are you afraid of heights? ( ) Yes ( ) No
An example of an open-ended question would be:
List the three things of which you are most afraid.
Both have pros and cons. Structured questions will provide you with data that you can compare across your entire sample. On the other hand, with structured questions you may leave out some common fears and thus miss out on collecting data on them. Open-ended questions may help you to discover common fears that you hadn't thought about. On the other hand, the responses may be hard to summarize, and you could have a hard time drawing conclusions. We recommend that the majority of your survey consist of structured questions, with perhaps one or two open-ended questions.
- In order to write your structured questions, you'll need to come up with a list of common fears appropriate for each age group that you intend to survey. One way to do this would be to start with a smaller survey! This could be as simple as an informal poll on the playground at recess. Try to compile a comprehensive list of common fears.
- Think about what type of response you want. Do you want a list of fears (simple yes/no responses) or do you want some kind of rating scale (e.g., a 0–4 scale: 0: not afraid at all, 1: a little afraid, 2: moderately afraid, 3: very afraid, 4: most frightening thing imaginable).
- You can use structured questions, open-ended questions, or both. An example of a structured question would be:
- When you've completed the questions for your survey, first try it out on a small group (5–10 people). Make sure that the questions are all clearly worded and understandable. Make any revisions that are needed, and then run the survey on the larger sample group.
Analyzing the Results
- The most convenient way to analyze your results will be to use a spreadsheet program, like Microsoft Excel or WordPerfect QuattroPro. Each column on the spreadsheet can represent one question on your survey, and each row on the spreadsheet will contain the responses from a single participant.
- You can use the spreadsheet program's formulas to count up the responses for each question. If you have simple yes/no questions, you can count the number of yes responses, and the total responses. If you have questions with a rating scale, you can use the spreadsheet to calculate how many respondents chose each rating (i.e., the relative frequencies of each response). The Science Buddies project Dry Spells, Wet Spells: How Common Are They? show show to use Excel's COUNTIF function to do this. There are also instructions on using Excel to make a frequency histogram, which you can use to show the survey responses graphically.
- Compare the results between the two age groups. Are some fears common to both groups? Are some fears unique to one of the groups?
- How many respondents did you have in each group? What can you say about the margin of error for your survey results?
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Variations
- More advanced students will want to perform calculations to determine whether differences between age groups are statistically significant.
- Analyze the survey responses by gender. What similarities and differences do see? Be sure that your sample population includes sufficient numbers of males and females.
- Expand the number of age groups for your study. You may need to re-design your survey to include appropriate questions for each age group. More advanced students will want to perform analyses of statistical significance across multiple groups. Finding a mentor with expertise in statistical analysis is recommended.
Careers
If you like this project, you might enjoy exploring these related careers:
