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

The drawings show some data involving three variables:

. D --- a quantitative variable

. A --- a quantitative variable

. G --- a categorical variable with two levels: S TEX COMMAND NOT FOUND K

Copy the above graph onto a piece of paper. On top of that sketch, you will be drawing functions specified by model formulas. For example:

Example: D ~ G.

Draw a function that shows the pattern of the fitted model values for each of the following models:

a. D ~ A + G

```{asis}

There are two linear components --- one for each level of G. But, since there is no interaction term, the lines must have the same slope.

#. D ~ A-1

    ```{asis}
![](Images/S2007-9-fig-ans3.png)  

The exclusion of the intercept term forces the line to go through the origin.

. D ~ A

```{asis}

A simple straight-line graph.

#. D ~ A*G

    ```{asis}
![](Images/S2007-9-fig-ans2.png)

By including an interaction term between A and G, the lines for each group can have different slopes.

. D ~ 1

```{asis}

This is the all-cases-the-same model. Since model doesn't depend on A or G at all, the graph is flat.

#. D ~ poly(A,2)

    ```{asis}
![](Images/S2007-9-fig-ans6.png) 

A second-order polynomial has a parabolic shape.  The fitted parameters set the location of the peak and the orientation ("bowl" or "mountain").

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