# Stat 3011 (Geyer) In-Class Examples (Standard Deviation)

## General Instructions

To do each example, just click the "Submit" button. You do not have to type in any R instructions (that's already done for you). You do not have to select a dataset (that's already done for you).

## The Normal Distribution

Non-Explanation: In the famous words of a comment in the source code for the UNIX kernel, "you are not expected to understand this".

What this code does is

• generate a random sample of size n from the standard normal distribution.
• plot its histogram, showing the sample mean and the sample mean plus or minus one sample standard deviation.
• plot the density curve of the standard normal distribution, showing the population mean and the population mean plus or minus one population standard deviation.
• according to the "68%-95% rule" of the textbook, about 68% of the sample lies between ticks on the horizontal axis on the upper plot. Maybe more, maybe less than 68% depending on how representative the sample is.
• exactly 68.26895% of the population lies between the ticks on the horizontal axis on the lower plot.