The paper "Turning to Learn: Screen Orientation and Reasoning from Small Devices" (Computers in Human Behavior [2011]: 793-797) describes a study that investigated whether cell phones with small screens are useful for gathering information. The researchers wondered if the ability to reason using information read on a small screen was affected by the screen orientation. The researchers assigned 33 undergraduate students who were enrolled in a psychology course at a large public university to one of two groups at random. One group read material that was displayed on a small screen in portrait orientation, and the other group read material on the same size screen but turned to display the information in landscape orientation (see figure below).

The researchers found that performance on a reasoning test that was based on the displayed material was better for the group that read material in the landscape orientation.

a. Is the described study an observational study or an experiment?

b. Did the study use random selection from some population?

c. Did the study use random assignment to experimental groups?

d. Is the conclusion-that reasoning using information displayed on a small screen is improved by turning the screen to landscape orientation- appropriate, given the study design? Explain.

e. Is it reasonable to generalize the conclusions from this study to some larger population? If so, what population?