## Samples and Populations

 Getting Started General Instructions | Introduction to Your Study | Experimental Design | Stating a Hypothesis Descriptive Statistics Histograms | Central Tendency | Standard Deviation | Confidence Intervals Comparing Two Samples Samples and Populations | Choosing a T-Test | Paired T-Test | P-Values and T-Tables Important Concepts The Normal Distribution | Z Scores | Probability Distributions Levels You are currently on Samples and Populations at level 2. Level 1 | Level 2 | Level 3 Next Topic Confidence Intervals | Choosing a T-Test

### Explanation

Sample Size
At level one we saw that a sample represents a small number of units taken from a larger population and that the larger the sample, the better it reflects the population. The term 'sample size' refers to the number of measurements in the sample. Now we will practice making some simple calculations based on sample size.

Sample size is always notated in statistics using the letter n. If you are aware of this fact and happy using n in calculations, you can skip this page and move on.

### Exploration

In the exploration stage of level two through out this tutorial you will be shown formulae and asked to make calculations guided by those formulae. Here are a few very simple formulae involving n to get you used to the idea. Hover over each one to see what it means.

### Application

Again, as preparation for later levels and to practice using the calculator, perform the following sums involving n. You have 20 data points in your data.
 For your data, what value is n? For your data, what value is n-1? Divide the number 20 by n and round the result to 2 decimal places using the [RD] button to round down.
Calculator
( You need to enable Java to see this applet. )
Help
 Confidence Intervals | Choosing a T-Test