A cognitive psychologist speculated that left-handed people would have better me

Question

A cognitive psychologist speculated that left-handed people would have better mental rotation ability than right-handed people, especially for difficult imagery tasks.  He gave a group of 20 right-handed subjects and 20 left-handed subjects the classic mental rotation task, where subjects view a pair of images that differ in their rotation from one another and decide whether they are the same or different.  Half the images can be rotated to become identical are the same; the other half is flipped images and can never be rotated to the same image.    On 100 trials, the two images were rotated between 15 and 60 degrees (the easy condition) and on another 100 trials the images were rotated between 120 and 175 degrees (the hard condition).   Each subject received the 200 trials in a random order uniquely determined for that subject.  The dependent variable was reaction time (RT) to decide if the images were the same or different.

Letting L and R stand for left and right handed, and E and D stand for easy and difficult, the mean reaction times (in msec) were as follows: LD 800, LE 700, RD 900, RE 800.

What type of research design was used?  How were subjects assigned to levels of the independent variables? Should there be any concern about carrying over effects for the within-subjects variable?  If so, how was this handled? Just looking at the group means, was there evidence for the main effect for handedness?   Was there evidence for the main effect of difficulty level?   Was there evidence for an interaction effect?

A cognitive psychologist speculated that left-handed people would have better mental rotation ability than right-handed people, especially for difficult imagery tasks.  He gave a group of 20 right-handed subjects and 20 left-handed subjects the classic mental rotation task, where subjects view a pair of images that differ in their rotation from one another and decide whether they are the same or different.  Half the images can be rotated to become identical are the same; the other half is flipped images and can never be rotated to the same image.    On 100 trials, the two images were rotated between 15 and 60 degrees (the easy condition) and on another 100 trials the images were rotated between 120 and 175 degrees (the hard condition).   Each subjects received the 200 trials in a random order uniquely determined for that subject.  The dependent variable was reaction time (RT) to decide if the images were the same or different.

Letting L and R stand for left and right handed, and E and D stand for easy and difficult, the mean reaction times (in msec) were as follows: LD 800, LE 700, RD 900, RE 800.

A cognitive psychologist speculated that left-handed people would have better mental rotation ability than right-handed people, especially for difficult imagery tasks.  He gave a group of 20 right-handed subjects and 20 left-handed subjects the classic mental rotation task, where subjects view a pair of images that differ in their rotation from one another and decide whether they are the same or different.  Half the images can be rotated to become identical are the same; the other half is flipped images and can never be rotated to the same image.    On 100 trials, the two images were rotated between 15 and 60 degrees (the easy condition) and on another 100 trials the images were rotated between 120 and 175 degrees (the hard condition).   Each subject received the 200 trials in a random order uniquely determined for that subject.  The dependent variable was reaction time (RT) to decide if the images were the same or different.

Letting L and R stand for left and right handed, and E and D stand for easy and difficult, the mean reaction times (in msec) were as follows: LD 800, LE 700, RD 900, RE 800.

Explanation / Answer

1. A mixed (both between and within) quasi-experimental design was used in the study.

2. The subjects were assigned to different levels of the independent variables: left handed easy condition, left handed difficult condition, right handed easy condition and right handed difficult condition.

3. In any within subjects design, there is a good chance that carryover effects due to practice or fatigue may have occurred.

4. In this study, the probability of carryover effects impacting the IV-DV relationship is quite low as the researchers randomised the order of presenting the easy and difficult trial conditions.

Please post the other questions separately as we are supposed to answer just one question or four sub parts of a question.

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