---
title: "Session 10 — Survey score as a random variable"
author: "Prof. Dae-Jin Lee (daelee@faculty.ie.edu)"
date: "Fall 2026"
output:
  html_document:
    toc: true
    theme: flatly
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE, message = FALSE, warning = FALSE)
library(tidyverse)
```

```{r}
survey <- read_csv("data/survey_attitudes.csv")
x <- survey$support_international_cooperation

c(mean = mean(x), sd = sd(x), var = var(x))
mean(x >= 7)
```

```{r}
tibble(x = x) |>
  ggplot(aes(x = x)) +
  geom_histogram(bins = 15) +
  labs(
    title = "Empirical distribution of cooperation support",
    x = "Support score",
    y = "Count"
  )
```

**Interpret:** mean = center of attitudes; SD = typical person-to-person spread.  
$P(X\ge 7)$ is an empirical probability in this teaching population.