`inference()`

functionBefore you can run the `inference()`

function, you need to check that you have the `ggplot2`

, `gridExtra`

, and `broom`

packages installed. If you installed the `tidyverse`

package, then you should already have `ggplot2`

and `broom`

, but you may not have `gridExtra`

installed. To check which packages you have available, copy and paste the following code snippet into your *Console* on RStudio:

```
installed.packages()[, "Package"][
names(installed.packages()[, "Package"]) %in% c("tidyverse", "ggplot2",
"gridExtra", "broom")]
```

If you have the packages, your output should look something like this:

```
broom ggplot2 gridExtra tidyverse
"broom" "ggplot2" "gridExtra" "tidyverse"
```

It’s okay if `tidyverse`

isn’t there but `broom`

and `ggplot2`

are. If you are missing any of the required packages, then you need to install them. For example, to install `gridExtra`

, you would run:

`install.packages("gridExtra")`

Once you have the necessary packages, move on to the next section.

`inference()`

functionThe `inference()`

function is stored in an RData file on the course website:

You can attempt to load it directly into your R session by running the following in your *Console* or *RMarkdown* file:

`load(url("http://fall17.cds101.com/R/inference.RData"))`

If that does not work, then you will need to download the file by clicking the above link. After downloading it, use your operating system’s file manager to find the downloaded file and move it to your working directory, such as your current Github repository folder. To double check that you moved it to the correct place, go back to RStudio, open your *Console*, and run:

`list.files()`

If you **don’t** see `"inference.RData"`

as one of the listed files, then run `getwd()`

in *Console* to check your current working directory. If this doesn’t match where you copied `inference.RData`

, then you need to move it to the directory printed out by `getwd()`

.

Once you have `inference.RData`

in the correct place, run the following to make `inference()`

available in R.

`load("inference.RData")`

`inference()`

documentationRun hypothesis tests on and compute confidence intervals for a response variable using either CLT-based or simulation-based methods.

Input | Default | Description |
---|---|---|

y | response variable, can be numerical or categorical | |

x | NULL | explanatory variable, categorical (optional) |

data | name of data.frame that y and x are in | |

type | c(“ci”, “ht”) | ci (confidence interval) or ht (hypothesis test) |

statistic | c(“mean”, “median”, “proportion”) | parameter to estimate: mean, median, or proportion |

success | NULL | which level of the categorical variable to call “success”, i.e. do inference on |

order | NULL | when x is given, order of levels of x in which to subtract parameters |

method | c(“theoretical”, “simulation”) | CLT based (theoretical) or simulation based (randomization/bootstrap) |

null | NULL | null value for a hypothesis test |

alternative | c(“less”, “greater”, “twosided”) | direction of the alternative hypothesis |

sig_level | 0.05 | significance level, value between 0 and 1 (used only for ANOVA to determine if posttests are necessary) |

conf_level | 0.95 | confidence level, value between 0 and 1 |

boot_method | c(“perc”, “se”) | bootstrap method; percentile (perc) or standard error (se) |

nsim | 15000 | number of simulations |

seed | NULL | seed to be set, default is NULL |

verbose | TRUE | whether output should be verbose or not |

show_var_types | verbose | print variable types, set to verbose by default |

show_summ_stats | verbose | print summary stats, set to verbose by default |

show_eda_plot | verbose | print EDA plot, set to verbose by default |

show_inf_plot | verbose | print inference plot, set to verbose by default |

show_res | verbose | print results, set to verbose by default |