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How to Find the Lower Quartile on a Number Line

The lower quartile is the number that comes in the 25th percentage on the number line. It is frequently found in a number line box plot. An easy way to think of the lower quartile is that it is the median of the numbers smaller than the median. The median represents the middle, 50 percent, number on your number line. You would use these terms primarily in statistics to analyze your data. Because these are basic terms, you should master them before moving to more complex statistics.

Instructions

- 1
  Write out your numbers on the number line.
- 2
  Find the number that comes in the middle of all the numbers. For example, if your number line has 1, 2, 3, 4, 5, 6 and 7, then 4 is in the middle. If two numbers are in the middle, add them together and divide by two. For example, if you number line has 1, 2, 3, 4, 5, 6, 7 and 8, then 4 and 5 are in the middle, so 4 plus 5 equals 9. Then, 9 divided by 2 equals 4.5. This is your median.
- 3
  Erase any numbers that are larger than or equal to the median; you do not need these.
- 4
  Find the middle number of the remaining numbers. Again, in the first example, if your number line has 1, 2 and 3 remaining, then 2 is in the middle. If two numbers are in the middle, add them together and divide by two. In the second example, if you number line has 1, 2, 3, 4 remaining, then 2 and 3 are in the middle, so 2 plus 3 equals 5. Then, 5 divided by 2 equals 2.5. This is your lower quartile.

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