Chapter 1.6 ­ Quartiles and Percentiles
September 18, 2012
Notes:
Activity ­ With your partner, complete the following #1­3.
TEST SCORES
58 84 72 40 95 78 92 98 82 50
67 90 75 93 87 55 84 86 62 67
1.) Find the median
2.) Find the median of the scores below the median and above the median.
Date: Chapter: Chapter 1:6 ­­> Quartiles and Percentiles
Objectives: Identify quartiles and calculate percentiles.
3.) Into how many equal parts do the three medians separate the scores?
*Quartiles (Q1, Q2, Q3) ­ Three numbers that group the data into four equal parts (25% each).
Types of Quartiles
Q1 ­ Median of lower set of data
Q2 ­ Median of the data
Q3 ­ Median of upper set of data
*Interquartile Range (IQR) ­ Range of Q3 and Q2
*Percentile ­ Indicates the percent of those who took the test and achieved at or below your score; measure of rank within a group.
­Ex: If your score is in the 83rd percentile, 83% scored less than or equal to
your and only 17% scored better.
How to find Percentile:
# of scores less than or = to your score
100 = percentile
total # who took the test
Ex. 3 ­ Find rank.
Examples:
Ex. 1 ­ Find the lower quartile, median, upper quartile and interquartile range.
18
29
56
42
58
31
40
28
37
You scored in the 80th percentile and there were 50 people who took the test.
46
Ex. 4 ­ Find the total number of people.
You scored in the 75th percentile. There were 47 people who scored less than you. Ex. 2 ­ Find the percentile.
a) Bernardo took a placement test in order to be accepted into a computer course. His score is 48th from the highest out of 760 who took the test. Find the percentile Bernardo ranked in.
Ex. 5 ­ Find the number who scored above and below you.
600 people took a test. You scored in the 67 percentile. Ex. 6 ­ Find the number who scored above you, below you, and your rank.
b) The following are the scores on Mrs. Van Hoose's last math test:
62 91 99 87 89 78 95 98 95 83 69 75 88 91
a) You were 1 of 300 that took a test and you were in the 90th percentile.
1. If you score an 83, what percentile are you in?
b) You were 1 of 250 that took a test and you were in the 84th 2. If you score a 99, what percentile are you in?
Integrated Math II
percentile.
Chapter 1.6 ­ Quartiles and Percentiles
Try These Exercises ­ p. 30 (#1, 2, 4, 5)
Complete the problems above and have me check them. If they are all correct, you will receive the homework assignment.
Integrated Math II
September 18, 2012