---
title: "Session 11 — One random sample"
author: "Prof. Dae-Jin Lee (daelee@faculty.ie.edu)"
date: "Fall 2026"
output:
  html_document:
    theme: flatly
---

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

Treat the CSV as a teaching population.

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

set.seed(11)
samp <- survey |> slice_sample(n = 40)
mean(samp$support_international_cooperation)
```

**Interpret:** one sample mean is close-ish to the population mean — but not identical. That gap is sampling error.