Effect of recall interval on decay in working memory

Plotting a Data Frequency Distribution Histogram

Tutorial Navigation 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 Frequency Histograms at level 3. Level 1 | Level 2 | Level 3 Next Topic Stating a Hypothesis | Central Tendency

Explanation Histogram Shapes When you look at a frequency histogram, you will see it has a certain shape. This fact is so useful that statisticians talk about the shape of the distribution of data in terms of the shape the histogram would make. On this page, we will look at some of the most common shapes and learn a little about their qualities. Here are 6 different histograms, each with a different shape. Flat (or Even) A flat histogram indicates that every value appears in the data the same number of times. If you rolled a die often enough, you would get a flat histogram. Nearly Flat A perfectly flat histogram is rare in practice unless you have very a large sample. A nearly flat histogram suggests that the population distribution is flat, but that the sample is not large enough to reflect that fact. Normal A normally shaped histogram indicates that the sample data has a normal distribution. There is a topic covering normal distributions in this tutorial. Bimodal A bimodal histogram has two peaks - showing two modes. This might suggest that there are two distinct populations, each with a different mode, represented in your one sample. Skewed Left A histogram with skew to the left (also called negative skew) indicates that the majority of the data has values towards the upper end of its range. Skewed Right A histogram with skew to the right (also called positive skew) indicates that the majority of the data has values towards the lower end of its range.

Exploration Use the game below to try and produce a histogram similar to each of those shown above. The numbers that you enter in the boxes are the raw data and not the histogram heights. Your challenge is to enter raw data that produces histograms with each of the following shapes: Flat Normal Positive Skew Negative Skew Bimodal ( You need to enable Java to see this applet. )

Application Here is the histogram for items correctly Recalled when recall Interval is 100 msecs. Look at your histogram and answer these questions about its shape: How flat is your distribution? Choose..Perfectly flatNearly flatNot flat   How would you describe the skew of this data? Choose..Little or no skewNegative skewPositive skew

Stating a Hypothesis | Central Tendency