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4.5 Central Tendency 131
1 def getMax(alist):
2 maxSoFar = alist[0]
3 for item in alist[1:]:
4 if item > maxSoFar:
5 maxSoFar = item
6
7 return maxSoFar
Listing 4.3 Alternative function to return the maximum value in a list
Exercises
4.14 Implement the getMin function using iteration by index.
4.15 Implement the getMin function using iteration by item.
4.16 Rewrite the getRange function using getMin and getMax.
4.5 Central Tendency
One of the most often used measures of a collection of data is known as central tendency
a process that estimates where the “center” of a collection will be found. There are three
common ways to compute central tendency: (1) mean, (2) median, and (3) mode.
4.5.1 Mean
The most common measure of central tendency is the mean also called the average.To
compute the mean, we simply add up the values in a collection and divide by the number
of items. Listing 4.4 shows how this is done. Given a list of values, we use the sum function
to compute a total and the len function to compute the number of values. The mean is
simply the sum divided by the length. Session 4.10 shows the mean function in action.
1 def mean(alist):
2 mean = sum(alist) / len(alist)
3 return mean
Listing 4.4 Computing the mean of a list

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