Effect of recall interval on decay in working memory

Samples and Populations

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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