02-class.Rmd

---
title: "Class 2: Regression and inference"
author: "Andrew Heiss"
date: "`r Sys.Date()`"
output:
  xaringan::moon_reader:
    lib_dir: "libs"
    chakra: "libs/remark-latest.min.js"
    css: ["default", "css/ath-slides.css", "css/ath-inferno-fonts.css", "css/animate.css"]
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---

```{r setup, include=FALSE}
knitr::opts_chunk$set(warning = FALSE, message = FALSE, 
                      fig.retina = 3, fig.align = "center")
```

```{r packages-data, include=FALSE}
library(tidyverse)
library(broom)
library(patchwork)
```

```{r xaringanExtra, echo=FALSE}
xaringanExtra::use_xaringan_extra(c("tile_view"))
```

class: center middle main-title section-title-3

# In-person<br>session 2

.class-info[

**August 29, 2022**

.light[PMAP 8521: Program evaluation<br>
Andrew Young School of Policy Studies
]

]

---

name: outline
class: title title-inv-8

# Plan for today

--

.box-6.medium.sp-after-half[R FAQs]

--

.box-5.medium.sp-after-half[Regression FAQs]

--

.box-2.medium.sp-after-half[Transforming data with **dplyr**]

--

.box-1.medium[Regression with R]

---

layout: false
name: r-faqs
class: center middle section-title section-title-6 animated fadeIn

# R FAQs

---

layout: true
class: middle

---

.box-6.large[RStudio fun]

---

.box-6.large[Column types]

.box-inv-6[Numeric, continuous, count, ordinal, interval,<br>qualitative, categorical, a billion other inconsistent names]

---

.box-6.large[File paths, working directories,<br>and RStudio projects]

???

- <https://www.theverge.com/22684730/students-file-folder-directory-structure-education-gen-z>
- Working directories and RStudio projects

---

.box-6.large[The hyperliterality of computers]

---

.box-6.large[R Markdown fun]

???

- Markdown metadata and outputs, figure sizes
- Show final Rmd products. Explanatory, like blog post code through or a problem set vs. stand-alone research paper

---

.box-6.large[Fun with histograms]

---

.box-6.large[Logging]

???

<https://stats.stackexchange.com/a/18639/3025>

---

layout: false
name: regression-faqs
class: center middle section-title section-title-5 animated fadeIn

# Regression FAQs

---

layout: true
class: middle

---

.box-5.large[Regression equations]

.box-inv-5[And is the intercept ever useful,<br>or should we always ignore it?]

???

<https://evalf22.classes.andrewheiss.com/slides/02-slides.html#38>

<https://www.andrewheiss.com/blog/2022/05/20/marginalia/#regression-sliders-switches-and-mixing-boards>

---

.box-5.medium.sp-after[Why use two steps to create a regression in R?<br>(i.e. assigning it to an object with `<-`?)]

.box-5.medium[Why use `tidy()`<br>from the broom package?]

???

Show model with `lm()`; show t-test with `t.test()`; show both through `tidy()`

Use **marginaleffects**

---

.box-5.medium[How was the 0.05 significance<br>threshold determined?] 

.box-5.medium[Could we say something is significant<br>if p > 0.05, but just note that it is at<br>a higher p-value?<br>Or does it have to fall under 0.05?]

---

.box-5.large[Why all this convoluted<br>logic of null worlds?]

---

layout: false
class: title title-5

# Different "dialects" of statistics

.pull-left[
.box-5.medium[Frequentist]

$$P(\text{data} \mid H_0)$$

.box-inv-5["Regular" statistics;<br>what you've learned<br><small>(and are learning here)</small>]

]

--

.pull-right[
.box-5.medium[Bayesian]

$$P(H \mid \text{data})$$

.box-inv-5[Requires lots of<br>computational power]

]

---

layout: true
class: middle

---

.box-5.medium[Do we care about the actual coefficients<br>or just whether or not they're significant?]

.box-5.medium[How does significance relate to causation?]

.box-5.medium[If we can't use statistics to assert causation<br>how are we going to use this information<br>in program evaluation?]

---

.box-5.large[What counts as a "good" R²?]

---

.center[
<figure>
  <img src="img/02-class/nice-plot-1.png" alt="Euler diagram" title="Euler diagram" width="45%">
</figure>
]

---

.center[
<figure>
  <img src="img/02-class/plot-diagram-prediction-1.png" alt="R2 prediction" title="R2 prediction" width="75%">
</figure>
]

---

.center[
<figure>
  <img src="img/02-class/plot-diagram-estimation-1.png" alt="R2 estimation" title="R2 estimation" width="75%">
</figure>
]

---

.center[
<figure>
  <img src="img/02-class/prediction-vs-estimation.jpg" alt="R2 estimation vs prediction" title="R2 estimation vs prediction" width="100%">
</figure>
]

---

layout: false
name: dplyr
class: center middle section-title section-title-2 animated fadeIn

# Transforming<br>data with dplyr

---

layout: false
name: ggplot
class: center middle section-title section-title-1 animated fadeIn

# Regression with R