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Lesson 3: Basic Descriptive Statistics
3 Calculating the Mean or Average < Back | Next >
The mean or average is the sum of all the data divided by the number of data points. Mathematically it can be represented by the following equation:

Xavg = ∑ (x / n)

Where X avg is the mean or average, ∑x is the sum of all the data and n is equal to the number of data points. We will now go over an example.

Example

Let’s assume the following 10 numbers are the diameters of trees in a treatment unit we sampled.

10.2, 6.5, 8.2, 9.6, 24.0, 16.6, 13.4 5.3, 6.7, 31.8

The average diameter would therefore be equal to which of the following:
A. 16.6
B. 13.2
C. 9.6
D. 24.0

Response:

The average or mean is a good indication of the center of the data if the data has a symmetric distribution. However if the distribution of the data is not symmetric or there are extremely high or low values the mean may not be the best choice for describing the center of the data.

LESSON 3
1 Overview
2 Intro to Descriptive Statistics
3 Calculating the Mean or Average
4 Calculating the Median
5 Calculating the Mode
6 Describing the Spread of Data
7 Calculating the Variance
8 Calculating the Standard Deviation
9 Graphical Representation of Data
10 The Stem and Leaf Plot
11 Review Questions
< Back | Next >

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