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Good Morning! . Unit 2- Measures of Central Tendency & Dispersion. Example Data Set. Measures of Central Tendency. Example 1. Example 2. 2. If the mean of a distribution of 12 numbers is 108, find the sum of the numbers. Example 3.

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Example 2
• 2. If the mean of a distribution of 12 numbers is 108, find the sum of the numbers.
Example 3

3. If the mean of a distribution is 18.6, and the sum of the numbers is 3720, how many numbers are in the distribution?

5-Number Summary

The 5-number summary consists of the minimum value, Q1, the median, Q3 and the maximum value.

- Q1 is the first quartile and is found by finding the median of the lower half of the data.

- Q3 is the third quartile and is found by finding the median of the upper half of the data.

1. min = 1
• 2. Q1 = 3
• (The lower half of the data is 1, 3, 3 and the median of 1, 3, 3 is 3.)
• 3. median = 5
• 4. Q3 = 7
• (The upper half of the data is 5, 7, 8 and the median of 5, 7, 8 is 7.)
• 5. max = 8
The Inter-Quartile Range (IQR)
• The Inter-Quartile Range (IQR) is the result of subtracting Q1 from Q3.
• In our data the IQR is 7 – 3 or 4. It shows us where the middle 50% of the data lie.
Example 4
• 4. Use the following data showing the number of shoes owned by seniors.

7, 9, 5, 21, 10, 10, 4, 12, 15, 8, 7, 8, 15, 20, 5, 20, 12, 3, 4, 12, 6

• a. put the numbers in order
• b. give the 5-number summary
• c. draw a box polt
• d. find the IQR
• e. put in an outlier (like 120) and redo to see the effect on mean and the 5 number summary
Due Today Before you Leave..
• Write your survey question for you project #1.
• In addition, include an explanation of
• 1. how you intend to collect your data, 2. who you are going to survey and
• 3. the purpose of your survey.
Closure
• Reminders
• • Project #1 is due on Friday, 9/5/08.
• and
• • Unit #2 Homework is due on Mon, 9/8/08

•The Unit 2 Test is one week from today on Tuesday, 9/9/08.