Center and Spread

Center and Spread

Learning Objectives:

Understand and Apply Center and Spread

Center and Spread

When a set of data presented with quantitative in nature, we can describe the distribution by looking at the Center and Spread.


Center is where most of the data is located. Different ways to measure Center are as follows:

1.     Mean: The “Mean” is the sum of the values in the set divided by the number of values in the set.

2.     Median: The “Median” is the middle value in a set when the values are arranged in numerical order.


Spread is a measure that how spread out the numbers are. Consistent data means all of the data are close to each other. The more inconsistent the data is, the more spread out the numbers are. Several ways to measure Spread are as follows:

1.     Range: The “Range” is the difference between the maximum value and the minimum value of the data set.

2.     Quartiles: The “Quartiles” are values that divide the data in quarters. The first quartile (Q1) is the median of the lower half. The third quartile (Q3) is the median of the upper half. The interquartile range (IQR) is Q3 - Q1.

3.     Standard Deviation: The “Standard Deviation” is a measure of variation based on measuring how far each data value deviates from the mean.




Hook Questions:

1.      What is Center? How to measure it?

2.      What is Spread? How to measure it?




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