IROVD - Measures of Center (Lesson)
Measures of Center
Two of the most common measures of center are the mean and median. Let, n be the number of data values in a data set.
Example
The April high temperatures (in degrees Fahrenheit) for five consecutive years in Rhode Island are listed below. Find the mean and median for the data set: 90, 86, 84, 92, 77
Find the mean:
Mean = [(90 + 86 + 84 + 92 + 77)/5] = (429/5) = 85.8
Find the median:
- Write the data values from least to greatest: 77, 84, 86, 90, 92
- The middle value is 86, so that is the median.
Watch this video to try a few more examples:
Mean and Median Practice
1. Leah's quiz scores are listed below. Find the mean and median of Leah's quiz scores: 88, 84, 85, 86, 90, 81.
2. Jerry recorded how many minutes of television he watched each week. Find the mean and median of Jerry's data: 35, 75, 25, 55, 60, 45, 70.
The median divides the data set into two halves. The first quartile (Q1) of a data set is the median of the lower half. The third quartile (Q3) is the median of the upper half.
3. Find the first and third quartile of the set of data: 3, 5, 1, 2, 8, 7, 9 10, 2, 4.
4. Find the first and third quartile of the set of data: 11, 12, 8, 9, 15, 14, 8, 10, 10.
Averages are often used to tell us how someone has done, or predict how they might do.
And there are times when we want to ensure our average meets a certain standard. Watch this video to see a problem like that:
5. Corey's is a basketball player and his goal is to average at least 15 points per game. Below are the scores for Corey's first 9 games. He has one game left, how many points should Corey try to score in this last game to meet his goal? 14, 16, 16, 13, 14, 15, 14, 14, 14.
6. Lauren has 6 quizzes in a semester and has made the scores below on the first 5 quizzes. What does Lauren need to make on her last quiz so that her quiz average is above 85%? 76, 84, 92, 91, 87.
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