In dtkaplan/MultipleChoice: Support for Multiple Choice Questions in Shiny

library(MultipleChoice)
if ( ! exists(".show_answers")) .show_answers <- TRUE
Scorekeeper <<- list(problem=NULL, attempts=NULL, score=NULL)

The graphic is part of a report describing a standardized test for college graduates, the Collegiate Learning Assessment (CLA). The test consists of several essay questions which probe students' critical thinking skills.

Although individual students take the test and receive a score, the purpose of the test is not to evaluate the students individually. Instead, the test is intended to evaluate the effect that the institution has on its students as indicated by the difference in test scores between 1st- and 4th-year students. The cases in the graph are institutions, not individual students.

Source: Council for Aid to Education, "Collegiate Learning Assessment: Draft Institutional Report, 2005-6" http://www.cae.org

There are three variables involved in the graphic:

. cla --- The CLA test score (averaged over each institution) shown on the vertical axis

. sat --- The SAT test score of entering students (averaged over each institution) shown on the horizontal axis

. class --- Whether the CLA test was taken by freshmen or seniors. (In the graph: blue for freshmen, red for seniors)

What model is being depicted by the straight lines in the graph? Give your answer in the standard modeling notation (e.g, A ~ B + C) using the variable names above. Make sure to indicate what interaction term, if any, has been included in the model and explain how you can tell whether the interaction is or is not there.

MC_question("C06_M105-1", 
            "cla ~ sat" = "What about the separate lines?",
            "sat ~ cla" = "sat is not the response variable",
            "cla ~ class" = "What's the continuous variable involved?",
            "cla ~ sat + class" = "**RIGHT**" ,
            "cla ~ sat * class" = "**RIGHT**",
            "sat ~ cla + class" = "sat is not the response variable", 
            "sat ~ cla * class" = "sat is not the response variable")

``{block echo = .show_answers} ANSWER: The response variable --- on the vertical axis --- is theCLA score. There is obviously a separate line for each group --- red or blue, referring to seniors or freshmen. The question is whether the lines are parallel or not. If the lines are not parallel, there must be an interaction term:cla~sat*class`.

If the lines are exactly parallel, the model is cla ~ sat+class, without an interaction term.

Examining the graph closely, it can be seen that the lines are not exactly parallel.

(Aside: Even a model with an interaction might give parallel lines, if it happened that the interaction term was not playing any role at all. But without an interaction term, the lines must be parallel.) ```

dtkaplan/MultipleChoice documentation built on May 15, 2019, 4:58 p.m.