Measures of Central Tendency

Chapter 13 Measures of Central Tendency

Learning Objectives
1 find the mean, median and mode of a set of ungroup data.
2 find the mean, median and modal class of a set of grouped data.

Title page story, oral and dictation
In a class od 39 students, the average weight is 39 kg. After a new student has joined the class, the average weight becomes 40 kg. What is the weight of this new student?

Hints
1 What is the total weight of the 39 students? 39 x 39kg 1521kg
2 After the addition of the new student, what is the total weight of the 40 students?
40 x 40kg 1600kg
3 Find the weight of the new student. 1600 - 1521 79kg

Preview
Basic technique

13.1 What is Central Tendency?
13.2 Means
13.3 Medians
13.4 Modes and Modal Classes
The mode of a set od data is the item with the highest frequency.

**Chapter Summary
1 Mean: Sum of all the data, number of data
2 Median
a For a set of n data arranged in ascending or decending order, if n is an odd
number, the median is the middle term, if n is an even number, the median is the mean of the two middle terms.
3 Mode and modal class

Additional Question
1 The following table shows the number of words in three passages, and the time
required for Sally to finish typing them up.
2 Choose a question you are interested in and conduct a statistical survey on it.
eg the number of late arrivals and absences in your class last month.

Repeat and check carefully again
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