1. Algebra I
Unit 1

2. What is the mean? The average of the numerical values in a data set.
How do we find the mean?
ADD up all the values and then divide the SUM by the number of values.

3. Let’s find Abby’s MEAN science test score.97 84
Add all
the values. 88
100 95 63
Divide the sum
by the number
of values. 73 86
783 9 ÷ + 97
The mean is 87
783

4. What is the median? The middle value of a data set.
How do we find the median?
LIST the values from LEAST TO GREATEST!!!
Find the middle value.
If there are TWO middle values, find the AVERAGE of the two and that is your median.

5. What is the median of these numbers?
29, 8, 4, 11, 19
Remember to always list your data from least to greatest!
4, 8, 11, 19, 29 11

6. What is the mode? The value(s) that occur the most.
How do we find the mode?
LIST the values from LEAST to GREATEST.
Find the value(s) that appear the most.
A set of data can have:
No mode
One mode
More than one mode

7. Which number is the mode?
1, 2, 10, 9, 9, 4, 9, 2
1, 2, 2, 4, 9, 9, 9, 10 9

8. What is the range?
The difference between the greatest and the least value in a set of numbers.
How do we find the range?
LIST the values from LEAST to GREATEST.
Find the smallest and greatest number.
Find the difference between these two numbers.

9. What is the range?
29, 8, 4, 8, 18
4, 8, 8, 18, 29
29 – 4 = 25

10. Interquartile Range Interquartile Range (IQR): IQR = Q3 – Q1
First Quartile (Q1): The median of the observations whose position in the ordered list is to the left of the location of the overall median.
Third Quartile (Q3): The median of the observations whose position in the ordered list is to the right of the location of the overall median.

11. Inter-Quartile Range = 9 - 5½ = 3½
Finding the median, quartiles and inter-quartile range.
Example 1: Find the median and quartiles for the data below.
12, 6, 4, 9, 8, 4, 9, 8, 5, 9, 8, 10
Order the data
Lower Quartile = 5½ Q1
Median = 8 Q2
Upper Quartile = 9 Q3
4, 4, 5, 6, 8, 8, 8, 9, 9, 9, 10, 12
Inter-Quartile Range = 9 - 5½ = 3½

12. Inter-Quartile Range = 10 - 4 = 6
Finding the median, quartiles and inter-quartile range.
Example 2: Find the median and quartiles for the data below.
6, 3, 9, 8, 4, 10, 8, 4, 15, 8, 10
Order the data
Lower Quartile = 4 Q1
Median = 8 Q2
Upper Quartile = 10 Q3
3, 4, 4, 6, 8, 8, 8, 9, , 10, 15,
Inter-Quartile Range = = 6