Lesson 3: Central Tendency

When we have histograms of different shapes, how can we use one number to describe the data?

            Negatively Skewed   Normal Distribution         Positively Skewed

“Skewed to the Left”           Symmetric     “Skewed to the Right”

Mode

One method could be the mode, the value in the dataset that occurs the most. Since histograms are composed of bins, however, the mode would be a range of values. Try matching the following modes with the correct histogram:

Mode 1: 20-25

Mode 2: 110-120

Mode 3: 150-160

Mode 1 belongs to the positively skewed distribution; Mode 2 to the negatively skewed distribution; and Mode 3 to the normal distribution. 

As the bin size decreases, the mode becomes more exact; as the bin size increases, the mode becomes more ambiguous. In non-uniform datasets, values are grouped around a particular area. This is where you see the hump of the distribution. For example, take the following dataset, visualized with a dot plot.

•			•		•	•	•	•
1	2	3	4	5	6	7	8	9	10

A histogram of this data with bin size 5 looks like this:

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Continue to Lesson 4, or select a lesson below.

Lesson 1: Introduction to Statistical Research Methods
Lesson 2: Visualizing Data
Lesson 3: Central Tendency
Lesson 4: Variability
Lesson 5: Standardizing
Lesson 6: Normal Distribution
Lesson 7: Sampling Distributions
Lesson 8: Estimation
Lesson 9: Hypothesis Testing
Lesson 10: t-Tests for Dependent Samples
Lesson 11: t-Tests for Independent Samples
Lesson 12: Intro to One-Way ANOVA
Lesson 13: One-Way ANOVA: Test significance of differences
Lesson 14: Correlation
Lesson 15: Linear Regression
Lesson 16: Chi-Squared Tests
Afterward
Index