Like all experimental designs, within-subject designs have limitations. But instead of focusing on disadvantages, please describe the advantages that a within-subjects design can bring. What might be a scenario in which choosing a within-subjects design would be more appropriate than a between-subjects (between-groups) design?

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  1. Within subject design has many advantages. One advantage is that it may be cheaper since the same participants are being used in each group, another advantage is that not as many participants are needed in comparison to a between subjects design. Also in a between subjects design, since there are different people in each group, there is individual differences that can possibly affect the results, however in a within group design, there is no individual differences because the same participants are being used per group. Within subject design can be used when wanting to compare and contrast something, this way there would be less confounds- or external factors/variables affecting the results. A study on food for example, you may want to compare two different recipes of the same dish (bad example, but I could not think of any others) so you give the same participants each dish, and ask them to record their reaction to each. You can then compare their results. If you were to use a between subjects design for this study, it would not be helpful because individual differences would affect the results, and also the participants cannot give their output on both of the recipes.

  2. A within-subjects design should be used when the same sample is being tested multiple times in separate trials. In other words, the performance of each participant is being tested over a series of sessions. For example, this design would be used when testing a new drug among a sample of participants. The researcher would record the effects of the drug for each participant and they would do this in multiple sessions. They would then compare all this data with one another, to test what effect the drug had over time. A between-groups design would not be appropriate for this situation because this design is used to test separate groups, instead of the same sample.

  3. A within-subjects design can bring along with it a few advantages. Less participants are required to participate in a study that uses a within-subjects design which decreases error variance and therefore provides a much more powerful statistical test. Additionally, participants are involved in each of the experimental conditions and so individual differences do not need to be a concern. Another advantage of within-subjects design is that because the same participants are used, results can be compared between the different conditions.

    A scenario in which it would be more appropriate to use a within-subjects design than a between-groups design is if a researcher wanted to test the effect that sleep has on mood. Experimental conditions can include: sleeping for 4 hours, 6 hours, and 8 hours. Participants will be placed randomly into one of the three groups and after sleeping the designated amount of time, they will fill out of a mood questionnaire. This will continue until all of the participants have been in each experimental group. Because the participants remain constant, this ensures that the difference in mood are not due to internal characteristics or behaviors.

    1. Hi,
      I believe that you stated all the points that are positively related to within-subject designs. You highlighted that each individual will be in all aspects of the experiment which could alleviate any worry or need to perform better or differently. Your scenario is also a very good example of within-subjects and interesting case as well.

  4. Hello,

    Among the advantages of within-subject designs when conducting a study are the following: since all subjects/participants are exposed to the independent variables at least one time during the experiment, this shortens the number of subjects/participants required for the study. A shorter amount of subjects/participants saves research time and increases the speed of finding results. Also, by reducing the sample, the odds of making a Type II error are fewer, which means obtaining a more compelling test of the impact of the independent on the dependent variable. An example of a within-subjects design would be researchers trying to find an answer on whether drinking coffee in the morning helps students do better in school. For this study, the researchers would randomly select a sample of ten college students. One day, the researchers would have the students drinking coffee prior leaving for school, and the following day they would have the same students not drinking coffee. Finally, the researchers would compare their daily performances to see whether caffeine has an impact on how well they do in school.

    1. Hi Peter!

      I believe you outlined the advantages of a within-subject design very well. I also wanted to point out that the reduction of Type II Error also makes the study more significant; therefore, a highly favorable study with even more favorable results! I also like your example about caffeine because it is a topic that is always being tested on, especially since there are so many opinions on how it affects the body.

  5. The advantages of using a Within-subjects designs is better than better than between-subjects design when you are trying to use the same group for multiple trials for an experiment. For example let’s say you are trying to find the best exercise to make people sore. You would get a sample of people and test them with pull ups one day, and then push ups another, and planks another day, at the end you would collect all the data from each of the separate trials but same group of people to see which exercise made them sore the most.

  6. It would be advantageous to perform a within-groups design to several reasons. First, there would be less of a demand for participants or subjects because each individual would be involved in each of the conditions. In addition, this design would be less time consuming. Within-groups experiments are also not subject to as great an error variance. Of the advantages, this would be the most significant. If the possibility of error variance is reduced, the results of the research would be more valid.

    If a researcher were to do a study about the effect of alcohol on one’s balance, they might prefer to do a within-subjects design. In this case, the researcher would be able to assess not only the variability in balance among several participants, but they would also be able to analyze the variability within each participant. There is less of a need for more people and therefore, the given task can be performed several times by each participant.

  7. Within-subject studies are advantageous because they are not only cost effective, but they are also more efficient in avoiding error variance. Since the same participants are being used to compare the impact(s) of the variable being researched, it is easy to rule out the idea the results may have something to do with the differences amongst the participants. One example of a research study where a within-subjects study is useful is when a researcher is trying to measure how effect last minute studying/pulling an all nighter before an exam is in comparison to resting the day before the exam and getting a full night of sleep. Using the same participants, the researchers do not have to worry about the comprehension levels of each individual. They can compare the data with each other and it will still be relevant to the study with little error variance.

    1. Hi,

      That is a great research study example and a within-subjects would definitely be more helpful in showing us the comparison between the two conditions. There is less error variance in a within-subjects design due to the fact that there are less participants.

    2. I found the example that you gave interesting especially because it somewhat has to do with what our second paper is about. I also like how you stated that by using the same participants the researchers do not have to worry about the comprehension levels of each individual since they are not switching the participants.

  8. I think one advantage of within-subject design study is that there can be a fewer number of participants tested. The same person’s behavior can be tested under two separate conditions and then be compared. For example, a researcher could be trying to test differences in memory by having the same group of people read a story in a noisy room and then a quiet room. This can help understand where the difference lies in each of the independent variables solely by using the same group of people.

    1. Hello Feiza,
      I think your example accurately portrayed a within-subjects design because emphasis was made on the powerful fact that the same group is used more than once for each independent variable making comparisons easier. I am curious to know the results of such the study you mentioned.

  9. In a within-subjects design, there is low error variance, whereas in a between-subjects design, since there are a lot of uncontrolled and external variables, there is a high error variance. It is difficult for us to see the effect for an independent variable when there is a high error variance. Another advantage of a within-subjects design is that there are fewer participants. Each participant performs a task in both of the experimental conditions which results in a shorter time to perform the experiment as well. It is easier to see any differences in a within-subjects design because each participant’s answer is compared to the other answer they give in the second condition being tested.

    A scenario in which a within-subjects design would be more appropriate than a between-subjects design is if a researcher is testing the effectiveness of a drug treating depression. In a within-subjects design, the researcher would first test the level of depression prior to the drug and then test again after the drug. This helps us to see the difference between before the drug and after. In a between-subjects design, the researcher might break the participants up into groups based on their gender. By doing this, the researcher will have two independent groups being tested, one for the females and one for the males. The within-subjects design makes it easier for the researcher to see the differences and there is a lower chance of error variance compared to the between-subjects design.

  10. A few of the advantages of a within-subject design include the lower error variance, low cost efficiency as well as low time efficiency as compared to an between-subject design. A lower error variance comes about because the researched uses the same participants over for each independent variable being manipulated. Therefore, any confounds pertaining to any differences among each participants are kept constant throughout the experiment as a whole. Using the same participants more than once maximizes time and cost efficiency because researchers don’t have to go through the hassle of finding additional participants which may mostly require additional resources including time and money. A scenario in which choosing a within-subjects design might be advantageous to a between-subjects design is for example when a researcher is measuring the effect of different types of exercises on memory. In the first condition subjects run on the thread mill for 20 minutes and take a memory test. In the second condition the same group of participants do yoga for 20 minutes and also take a memory test of equivalent difficulty. Here the within-subjects design helps to maintain the variability that can distinguish one subject from another. Therefore facilitating researchers ability to compare the scores of the two memory test.

  11. Although the within-subject Design may have several limitations such as participants with demand characteristics, there are still many advantages it serves as well. For one, depending on the study, a certain amount of participants may be required. In this case, if a study requires a limited amount of participants, a within-subjects design is favorable. Thus, smaller participant group also equals less time involved as each participant is tended to faster. Also, each participant has the option whether they want to participate under every condition of the study. This is beneficial because when analyzing data, there can be comparisons between participants and the conditions they performed. Furthermore, an important advantage of this design is that there is a low error variance which essentially allows a very tight space for Type II error to occur, thus the results are very significant.

  12. Although the within-subject design may have several limitations such as participants with demand characteristics, there are still many advantages it serves as well. For one, depending on the study, a certain amount of participants may be required. In this case, if a study requires a limited amount of participants, a within-subjects design is favorable. Thus, smaller participant group also equals less time involved as each participant is tended to faster. Also, each participant has the option whether they want to participate under every condition of the study. This is beneficial because when analyzing data, there can be comparisons between participants and the conditions they performed. Furthermore, an important advantage of this design is that there is a low error variance which essentially allows a very tight space for Type II error to occur, thus the results are very significant.

    A scenario most suitable for using the within-subject design may be treating a disorder, such as ADHD and medication trails. Participants can be given a medication for ‘x’ amount of days and have their behaviors be recorded, then stop the medication completely. These results can be therefore compared and analyzed to see what effect the medication had on the disorder.

  13. There are many advantages to a within-subject design. First the number of participants or sample size can be smaller, for a between-subject design you would normally need enough participants to separate into the control and experimental groups while within-subjects design can utilize the same participants. Another benefit is that there’s a lower error variance because participants or subjects are a part of the control and experimental groups. This helps rule out confounds that come from the differences among participants or subjects. Because there is a lower error variance, within-subject designs are more powerful in detecting differences which reduces the likelihood of a type II error (a false negative, believing that difference do not exist when they do). An experiment that would be more appropriate in a within-subject design may be looking at how stress affects caffeine intake, because participants can vary in caffeine consumption on a daily basis separating into a control and experimental group would not accurately show the relationship between stress and caffeine consumption.

  14. There are many advantages in using advantages a within-subjects design as oppose to using between-subjects design. One of the many advantages may include that fewer participants are required, take less time, and most importantly the error variance is reduced. By having the error variance reduced, this not only means that the test is more powerful but also it is easier to detect a significant effect in the variable. A scenario in which a within-subjects might be the best fit is in a study which we may want to see the effects music has on concentration. This might be the best way to do so because we want to test these participants more than once and compare their scores in order to see the effects. By using a between-groups design, we would have at least one group not getting the treatment. For the case of music and concentration, we would want all the participants to get equal treatment in order to get the appropriate results.

  15. Within-subjects is a kind of experimental design where the same group of participants is exposed to all the different treatments in an experiment. I think within-subjects provides researchers with a more powerful statistical test of the hypothesis by reducing errors. Another advantage of within-subjects designs is that it requires fewer participants and it often takes less time. It is also easier to find a significant difference with a within-subjects design than with a between-groups design. For example, you are testing to find out which type of study skill will help certain participants get a better exam grade. You have writing notes, recording lecture and watching videos of the topic as the skills. Now you will make all same participants do all three types of skills and asses which helped them get the highest score on an exam.

  16. Some advantages of a within-subjects design study would be the low number of people being studied and therefore a less of a chance that some of the error found in the study is chalked up to the sheer number of people, and other logistical problems, such as limited time and/or money. By definition, a within-subjects design would most likely require less people than a between-subjects because it’s only one group of subjects being studied on over and over. As a result, this design can be flexible when time and funding is not. Another benefit of keeping the sample size small is the reduced chance of finding error due to a larger number of people in a study. That is, the pool would have a less of a chance to be random.
    Studies that are meant to track the improvement of the subjects over time would benefit more from a within-subjects design, where it would be necessary to study the same group as they improve.

  17. There are many benefits to a within subjects design. One of the many benefits is the fact that it is cheaper. Because you are testing the same subjects twice, you required half the subjects for the experiment than a between-subjects design; thus, reducing the cost of your experiment significantly. Another benefit to a within-subjects design is that error variance is reduced. Since you are test ting the exact same people again the people act as their own control group and variance error is reduced as a result. Reduction of variance error is an important factor because it makes your data much more powerful. Your chance of making a type II error drops and you more likely to reject the null hypothesis

    1. George,
      I agree entirely with the advantages that you listed for a within subjects design, the reduction or error and the reduction of costs, I just wanted to point out that the SQ also called for an example of an instance in which conducting a within subjects design would be better than a between subjects design.

  18. there are several advantages in conducting a within-subjects design experiment, some of which include the fact that there is less error since you are testing the same group several times. Another being the fact that you do not need an exhaustive amount of people to partake in your study as compared to doing an experiment with multiple groups.
    An example of when you could use a within-subjects design experiment is when you are testing different methods of achieving the same outcome. For example, you could use one group and see how different approaches to studying affects their exam scores.

  19. A within-subjects design has many advantages. First off, this design is a way to reduce error variance due to the fact that it uses fewer participants as opposed to a between-subjects design. By reducing the error variance, the study becomes much more powerful. Becoming more powerful reassures the experimenters that their chance of making a type II error significantly decreases. Within-subjects designs also take much less time. Subject variables are held constant throughout the entire study. This design is very common among researchers because of its many advantages.
    An example used in the book is an experiment based on the effects that colors have on mood. Giving participants a mood-rating task after sitting in a blue room for a certain amount of time and then comparing that to their answers on the same task after sitting in a red room for the same amount of time. In a between-subjects design, this would take double the amount of participants that a within-subjects design would.

  20. A within subjects design presents several advantages, one of which includes less room for response error considering the same group of people are participating. Another few advantages are how it is cost effective (less materials needed) as well time effective (testing one group could be much faster than several different ones).
    An example of an within subjects design experiment could be to test if SAT scores are effected by caffeine intake. A group of students could take the SAT after ingesting, no caffeine as a control group. Then take the exams again for each time participants ingested controlled levels of caffeine and compare those scores.

  21. The reason why a scenario like the one I mentioned is more appropriate as a within subjects design rather than a between subjects design is because by having different groups of people take tests with different levels of caffeine, there are many confounding variables including different individual reading, math and writing levels.

  22. Within-subjects design provides several advantages for researchers who use it. This design allows for a reduction in error variance and a study in which all subjects are exposed to each independent variable. Due to the reduction in error variance, it allows for the experiment to have a more powerful result. The design requires a smaller amount of participants and also a shorter length of time.
    An example of a within-subjects design would be trying to find out whether exercise effects scores on math tests. There would be own group of participants, and they would perform first a single exercise and then take a math exam. The second time the same participants will perform a different exercise and take the math exam. After that the researchers will calculate the results and see if either exercise supports the ability to do better on math exams.

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