---
title: "Session 12 — Two-group hypothesis test"
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")

two <- survey |>
  filter(education %in% c("Bachelor", "Postgraduate"))

two |>
  group_by(education) |>
  summarise(n = n(), mean_support = mean(support_international_cooperation),
            .groups = "drop")

tt <- t.test(support_international_cooperation ~ education, data = two)
tt
```

**Identify:** group means, estimated difference, CI, p-value.  
**Then ask:** statistically noticeable? substantively important? causal?