My project is about who can hold their breath longer, smokers or non-smokers. I have created a short questionnaire (how long do/did you smoke, do you consider yourself in good health?) and have three control groups: smokers, non-smokers and smokers who no longer smoke. I then time each person to see how long they can hold their breath. My data (actual time people can hold their breath) is all over the place because there are so many factors that can influence the study. These factors can be age, male or female, being tall or short, how much exercise a person gets, if they are overweight and so forth. These are factors I can not change and have no control over. What types of variables are these? I must identify these in my project, but what do I call them?
Any assistance you can give is greatly appreciated... my data is due Friday the 20th! Thanks so Much! Beowulf
I need help with variables portion of my project!
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ChrisG
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Re: I need help with variables portion of my project!
Hi Beowulf,
Welcome to the Ask an Expert forum. You have an interesting experiment. These sorts of factors are called "uncontrolled variables'. If you have many experimental subjects (such as in university research projects), you can try to control these variables by considering people with similar weight, height, etc, but I expect that will not be possible for your school project. Does that answer your question? If there is more you'd like to know please ask!
Chris
Welcome to the Ask an Expert forum. You have an interesting experiment. These sorts of factors are called "uncontrolled variables'. If you have many experimental subjects (such as in university research projects), you can try to control these variables by considering people with similar weight, height, etc, but I expect that will not be possible for your school project. Does that answer your question? If there is more you'd like to know please ask!
Chris
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Beowulf
- Posts: 3
- Joined: Tue Mar 11, 2008 6:30 am
- Occupation: Student
- Project Question: Who can hold their breath the longest, smokers or non-smokers?
- Project Due Date: 3/21/08
- Project Status: I am finished with my experiment and analyzing the data
Re: I need help with variables portion of my project!
Chris,
Thanks for your quick response. Is it that simple? Would I list these things in my conclusion stating the study could have been different with different test subjects? Because obviously it would have. Or, the conclusion would have been different if I had narrowed my test subjects for instance only using males or females, or only using people of a certain age group or certain height, right?
My project says I must list which type of variable I have independent, dependent or controlled. I was a little confused, but I think I have both independent and dependent. Because things like being male and how tall you are can't be changed. These are independent. Being overweight and a person who exercises is dependent because it can change, right? The rest are as you say, uncontrolled?
Thanks for your quick response. Is it that simple? Would I list these things in my conclusion stating the study could have been different with different test subjects? Because obviously it would have. Or, the conclusion would have been different if I had narrowed my test subjects for instance only using males or females, or only using people of a certain age group or certain height, right?
My project says I must list which type of variable I have independent, dependent or controlled. I was a little confused, but I think I have both independent and dependent. Because things like being male and how tall you are can't be changed. These are independent. Being overweight and a person who exercises is dependent because it can change, right? The rest are as you say, uncontrolled?
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ChrisG
- Former Expert
- Posts: 1019
- Joined: Fri Oct 28, 2005 11:43 am
- Occupation: Research Hydrologist
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- Project Status: Not applicable
Re: I need help with variables portion of my project!
Beowulf,
I would recommend reading this page, which discusses the different types of variables:
http://www.sciencebuddies.com/science-f ... bles.shtml
"The independent variable is the one that is changed by the scientist." This does not mean that you change whether or not someone is a smoker. It just means that you manipulate that variable by grouping people into smokers and nonsmokers.
"The scientist focuses his or her observations on the dependent variable to see how it responds to the change made to the independent variable." The length of time that people held their breath is the dependent variable, because you tested how this value differed depending on whether a person smokes or not.
The terms "dependent" and 'independent" do not relate to whether a person can change one of their physical attributes. Even if a person can not change their height, that could be a dependent variable in a study of how, for example, nutrition affects a persons height. The person cannot control their own height, but the scientist tries to control all other variables (gender, smoking, race, etc) and to look at people with different nutrition and different height to determine how nutrition can change a persons height, all other things being equal.
I'm not sure what you mean by "the study could have been different with different test subjects". Ideally, your experiment would give the same general results even if you chose a different group of study subjects. If your results change when you rerun the experiment, it might indicate that there is a problem such as an insufficient number of test subjects in the first experiment. Conversely, although a person can change their weight, their weight would be an independent variable in a study of how weight affects occurrence of heart disease.
I don't know your results well enough to know exactly what you should write in your conclusions. If you did not see a difference between smokers and non-smokers, you could say that the results did not support your hypothesis (if your hypothesis was that smokers would not hold their breath as long). You could add that this may be due to factors such as age, fitness, etc, that may also affect ones ability to hold ones breath, and that additional experiments that control those variables might give different results. You may or may not want to discuss variables as being "uncontrolled" because it sounds as though your teacher has not introduced this idea. You should ask your teacher. As noted above, the number of subjects could also be a factor. In scientific studies, hundreds or thousands of subjects may be required to test these kinds of hypothesis where there are many influential factors such as weight, height, etc.
As a side-note, these terms "independent" and "dependent" come from the idea that the independent variable is not affected by the dependent variable, and that the dependent variable is affected by (or depends on) the independent variable. For example, it makes intuitive sense that if you smoke, your lung capacity will be somewhat reduced, but it is unlikely that ones lung capacity would affect ones decision to smoke or not. However, in many studies, the relationships can be much more complicated, and the idea of one variable actually being "independent" isn't as clear. In any study, it is worth asking the question of whether your "dependent" variable could actually be affecting your "independent" variable. You have already done a good job of considering what other variables might influence results.
I hope that helps.
Chris
I would recommend reading this page, which discusses the different types of variables:
http://www.sciencebuddies.com/science-f ... bles.shtml
"The independent variable is the one that is changed by the scientist." This does not mean that you change whether or not someone is a smoker. It just means that you manipulate that variable by grouping people into smokers and nonsmokers.
"The scientist focuses his or her observations on the dependent variable to see how it responds to the change made to the independent variable." The length of time that people held their breath is the dependent variable, because you tested how this value differed depending on whether a person smokes or not.
The terms "dependent" and 'independent" do not relate to whether a person can change one of their physical attributes. Even if a person can not change their height, that could be a dependent variable in a study of how, for example, nutrition affects a persons height. The person cannot control their own height, but the scientist tries to control all other variables (gender, smoking, race, etc) and to look at people with different nutrition and different height to determine how nutrition can change a persons height, all other things being equal.
I'm not sure what you mean by "the study could have been different with different test subjects". Ideally, your experiment would give the same general results even if you chose a different group of study subjects. If your results change when you rerun the experiment, it might indicate that there is a problem such as an insufficient number of test subjects in the first experiment. Conversely, although a person can change their weight, their weight would be an independent variable in a study of how weight affects occurrence of heart disease.
I don't know your results well enough to know exactly what you should write in your conclusions. If you did not see a difference between smokers and non-smokers, you could say that the results did not support your hypothesis (if your hypothesis was that smokers would not hold their breath as long). You could add that this may be due to factors such as age, fitness, etc, that may also affect ones ability to hold ones breath, and that additional experiments that control those variables might give different results. You may or may not want to discuss variables as being "uncontrolled" because it sounds as though your teacher has not introduced this idea. You should ask your teacher. As noted above, the number of subjects could also be a factor. In scientific studies, hundreds or thousands of subjects may be required to test these kinds of hypothesis where there are many influential factors such as weight, height, etc.
As a side-note, these terms "independent" and "dependent" come from the idea that the independent variable is not affected by the dependent variable, and that the dependent variable is affected by (or depends on) the independent variable. For example, it makes intuitive sense that if you smoke, your lung capacity will be somewhat reduced, but it is unlikely that ones lung capacity would affect ones decision to smoke or not. However, in many studies, the relationships can be much more complicated, and the idea of one variable actually being "independent" isn't as clear. In any study, it is worth asking the question of whether your "dependent" variable could actually be affecting your "independent" variable. You have already done a good job of considering what other variables might influence results.
I hope that helps.
Chris
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Beowulf
- Posts: 3
- Joined: Tue Mar 11, 2008 6:30 am
- Occupation: Student
- Project Question: Who can hold their breath the longest, smokers or non-smokers?
- Project Due Date: 3/21/08
- Project Status: I am finished with my experiment and analyzing the data
Re: I need help with variables portion of my project!
Chris,
Just wanted to thank you again for your help with my project. And, to let you know that I won first place at my school. My project went to our county science fair where it competed against six other primary schools and 40 other 3rd grade projects. I won first place at the county fair as well. They were very impressed with the research I had done. And a lot of that research was done on this site. Thank you so much!! Beowulf
Just wanted to thank you again for your help with my project. And, to let you know that I won first place at my school. My project went to our county science fair where it competed against six other primary schools and 40 other 3rd grade projects. I won first place at the county fair as well. They were very impressed with the research I had done. And a lot of that research was done on this site. Thank you so much!! Beowulf
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ChrisG
- Former Expert
- Posts: 1019
- Joined: Fri Oct 28, 2005 11:43 am
- Occupation: Research Hydrologist
- Project Question: n/a
- Project Due Date: n/a
- Project Status: Not applicable
Re: I need help with variables portion of my project!
Beowulf,
Congratulations! It sounds like there were lots of reasons to celebrate. Also, thanks for letting us know how it went with your project. It is always helpful to get feedback about the Science Buddies site and about this forum.
I hope you enjoyed the experience and I look forward to working with you again on your next science project.
Chris
Congratulations! It sounds like there were lots of reasons to celebrate. Also, thanks for letting us know how it went with your project. It is always helpful to get feedback about the Science Buddies site and about this forum.
I hope you enjoyed the experience and I look forward to working with you again on your next science project.
Chris