Experiment design parameters.I have a doubt identifying the elements of the following experiment design:A study wants to determine whether users perceive the difference while playing a game at 30 fps or 60 fps. In the game the player has to destroy objects that traverse the screen. All subjects played a first part at 30 fps, a second part half of them played at 30 fps and the other half at 60 fps and finally the two halves interchanged roles.Here I understand that fps is an independent variable of the experiment and that the experiment is a "within subjects" one.After the game, we ask them if they perceived a difference between the equality of the three parts and in affirmative case we ask which image was the best. We register their score at the end of each part and their responses to which was the best image. In each condition, half of the subjects used a standard resolution screen and the other half used a high resolution screen.From here I deduce that the score is a dependent variable and I hope that the perceived quality of the image is another dependent variable (later on response time appears as a third dependent variable?). I have doubts whether the resolution of the screens is a second independent variable.We verify that visual accuracy doesn't change between the two groups. We register each action of the subjects during the game. The results show that globally the subjects aren't capable of telling what part of the game had higher fps but the scores were higher at 60 fps.So this part states that the visual accuracy is a controlled variable and that the principal effect of the experiment was that score was better when using higher fps.The response time (duration between the apparition of an object and first action of the subject) were shorter after 60 fps, but only for players with a high screen resolution.This should be an interaction effect between but there is no dependent variable stated.Therefore my explanation of the experiment doesn't fit the solution expected. Could you please point me what I'm missing here? I should be able to state:Two independent variablesTwo dependent variablesAn intermediate variable.A controlled variable.A principal effect.An interaction effect.

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Experiment design parameters.I have a doubt identifying the elements of the following experiment design:A study wants to determine whether users perceive the difference while playing a game at 30 fps or 60 fps. In the game the player has to destroy objects that traverse the screen. All subjects played a first part at 30 fps, a second part half of them played at 30 fps and the other half at 60 fps and finally the two halves interchanged roles.Here I understand that fps is an independent variable of the experiment and that the experiment is a &quot;within subjects&quot; one.After the game, we ask them if they perceived a difference between the equality of the three parts and in affirmative case we ask which image was the best. We register their score at the end of each part and their responses to which was the best image. In each condition, half of the subjects used a standard resolution screen and the other half used a high resolution screen.From here I deduce that the score is a dependent variable and I hope that the perceived quality of the image is another dependent variable (later on response time appears as a third dependent variable?). I have doubts whether the resolution of the screens is a second independent variable.We verify that visual accuracy doesn&#039;t change between the two groups. We register each action of the subjects during the game. The results show that globally the subjects aren&#039;t capable of telling what part of the game had higher fps but the scores were higher at 60 fps.So this part states that the visual accuracy is a controlled variable and that the principal effect of the experiment was that score was better when using higher fps.The response time (duration between the apparition of an object and first action of the subject) were shorter after 60 fps, but only for players with a high screen resolution.This should be an interaction effect between but there is no dependent variable stated.Therefore my explanation of the experiment doesn&#039;t fit the solution expected. Could you please point me what I&#039;m missing here? I should be able to state:Two independent variablesTwo dependent variablesAn intermediate variable.A controlled variable.A principal effect.An interaction effect.

browarodfv · Accepted Answer

I agree with you that score and perceived image quality are dependent variables. It seems to me that response time is also a dependent variable. I am not familiar with the purpose of the experiment; possibly the &#039;principal&#039; effect is score.Independent (design) variables are fps, screen resolution, and order (first vs. second part). Order may be important if practice alters responses (dependent variables). These are &#039;fixed&#039; effects. Subjects are a random effect, which needs to be taken into account because subjects respond under various circumstances (combinations of independent variables).A possible interaction effect would occur if scores were not &#039;additive&#039; with respect to fps and resolution. For example, if scores are higher for more fps at low resolution but not at high resolution.I have no idea what you mean by &#039;intermediate variable&#039; or &#039;visual accuracy&#039;. Also, from your description of the experiment, I&#039;m not sure I understand it well enough to write a model for the experiment. For example, I am not quite sure when each subject uses hi vs low resolution screens and when each subject is exposed to fast vs. slow refresh rate, or in what combinations. Unless you have a hundred or so subjects, I&#039;d guess you are trying to look at too many independent variables to get decent power (probability of detecting real differences).

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