Hand-in Assignment for Chapter 1

Athletes routinely swipe black grease under their eyes to help cut down on glare on sunny days. Recently, some athletes have switched from grease to patches of black tape. Does either method work? Which is best? A recent study in the Archives of Ophthalmology, helped to answer these questions. A sample of 46 subjects were tested using the Pelli-Robson contrast chart, which gives a numerical rating for ability to discern contrast against a sunlit background. Subjects were then randomly assigned to one of three groups and tested again. One group used black grease, one used black tape, and one used clear petroleum jelly. The group wearing the black grease was the only group to show significant improvement in discerning contrast in sunlight.

1) Is this an experiment or an observational study? Explain.

It is an experiment because an experiment controls one or more of the explanatory variables. In the experiment above the subjects were randomly assigned to one of three groups and the variables were controlled.

2) Why is this study not double-blind (or even single-blind)?

The players would know whether they had tape or jelly on their face, and therefore it couldn’t possibly be a blind study let alone a double blind study.

3) What are the variables in the study? Identify each as either categorical or quantitative.

The variable of whether the players got black grease, black tape, or petroleum jelly is the categorical variable. The results from the Pelli-Robson contrast chart for each variable is the quantitative variable.

In a study, reported in Journal of Information Systems Education, investigating how students use their laptop computers in class, researchers recruited 45 students at one university in the Northeast who regularly take their laptops to class. Software was installed on each of their computers that logged information on the applications the computer was running, including how long each was open and which was the primary focus on the monitor. Logs were kept over multiple lectures. On average, the students cycled through 65 active windows per lecture. With one student averaging 174 active windows per lecture! The researchers developed a rubric to distinguish productive class-related applications from distractive ones, such as email and social networking sites. For each student, they recorded the percent of active windows that were distractive and the percent of time spent on distractive windows. They found that, on average, 62% of the windows students open in class are completely unrelated to the class, and students had distracting windows open and active 42% of the time, on average. Finally, the study included a measure of how each student performed on a test of the relevant material. Not surprising, the finds that the students who spent more time on distracting websites generally had lower test scores.

4) What are the cases in this dataset? What is the sample size? Is the sample a random sample?

The cases in the data set are the windows that the students had open during lectures for classes. They looked at 45 students who normally brought their laptops to class and what they did during the class on their laptop. This is not a random sample.

5) Is this an experiment or an observational study? Explain.It is an observational study because they do not control any of the variables. They simply look at 45 people who take their laptops to class and what they search/look at during the class. Everything is based off the observation of the data collected. There is no independent or dependent variable.

6) From the description given, what variables are recorded for each case? Identify each as categorical or quantitative.

The variables that are recorded are: The number of windows looked at during the lecture (Qualitative), the relevance of that window to the class material (categorical), How long the students spent on the distracting websites (qualitative), and how well the students did on tests/quizzes (qualitative)

7) The last sentences of the paragraph describes an association. What is the explanatory variable? What is the response variable?

Explanatory Variable: Time on distracting websites while in class

Response Variable: How well the students did on the test

8) From the information given, can we conclude that students who allocate their cognitive resources to distracting sites during class get lower grades because of it? Why or why not?

I would say no. Since the study was conducted looking at 45 students there is no way to verify whether all bias was removed the experiment. Since the students selected were not chosen at random, and all of them knew that they were being monitored it could have some impact on the results and therefore the data resulting from the test could be skewed. They also do not mention when during the year they took the logs from. If it was in the earlier parts of the semester before a lot of homework and projects were given then it would be understandable to see the students on their laptops more requently, where as right before a test they might be on distracting websites less. This is unknown and thus we can’t determine if the distracting websites affected their performance in the class

9) Describe the design of a study that might allow us to make the conclusion in the previous question. Comment on the feasibility of conducting such a study.

If the students were given a laptop to use for a semester with the program already installed on it, and then out of the students that received the laptops a random selection of them were looked at and based off their use of the laptop in class. There would also have to be logged information for the entire semester. This way we could potentially determine other patterns and not just have a few weeks of looking at the students use of the laptop in class. Pulling of a study like this would be difficult but possible. Universities give laptops to students all the time so giving it to them with the program would be easy. The hard part would be determining if they use their laptops in class and if so then randomly collecting a sample from the students that do. It would be a complicated process but quite possible. The more variables that are looked at the tougher the experiment is to pull off.