Chapter+3

__**Central Tendency**__ Remember... mean, median, and mode have not changed since junior high. __Mean__ is the average (add 'em and divide by how many there are). __Median__ is the middle number, when they are in order. If the list has an even number of number, the median is the average of the "two middles". __Mode__ is the most occurring, there can be no mode, only one mode, or multiple modes.

//Examples:// {3,4,5,6,7} median is 5 {3,6,9,12} median is (6+9)/2 = 7.5 {1,2,3,4} no mode {1,2,2,3,4,4} mode 2 and 4 {1,1,2,2,3,3,4,4} no mode

__**Variation**__ Range is just maximum - minimum

Standard Deviation: 5 steps to glory. 1. take each data value minus the average 2. square each answer from step one 3. add the answers from step two together (ssx or sum of squares) 4. divide the answer from step 3 by one less than how many numbers there are in the set (variance) 5. square root the answer from step four. //(now pat yourself on the back)//

__**Position**__ The 5 number summary: Q0 = min, Q2 = median, Q4 = Max. Q1 = the middle of the first half, Q3 = middle of the second half.

Ex: {1,2,3,4,5} Q0=1, Q2=3, Q4=5.For Q1, ignore the 3 and find the middle of 1 and 2 --> Q1=1.5 For Q3, ignore the 3 and find the middle of 4 and 5 --> Q3=4.5

Ex: {1,2,3,4,5,6,7} Q0=1, Q2=4, Q4=7. Q1 would be 2 (ignore the 4) and Q3 would be 6 (again, ignore the 4)