Statistics Flashcards
Average
Sum / N of terms
Sum
Average * N of terms
Median
Middle number
For odd number sets, it is a unique number
For even number sets, it is the arithmetic average of the middle two numbers
Standard deviation
Average Spread
Small SD - closely clustered around average
Large SD - widely spread out, some points far from average
Algebraic Weighted Average
Weighted Average = component 1 (weighting 1) + component 2 (weighting 2)
Teeter-Totter Method
Draw teeter totter
If needed, calculate average if equal weightings
Determine which side weighs more
Calculate the difference between the two weighted items (the span of the teeter totter)
Calculate how much of the difference belongs to the heavier side (or to the lighter side)
Find proportion of the amount owned by either side over the total difference between the two sides (if looking for weighting of one or both of the two parts)
or
Count from the lighter side up the portion that belongs to the heavier side (if looking for the new weighted average)
Consecutive Integers
Counting up, consecutively (special set of consecutive multiples where the increment is the integer 1)
Consecutive Even Integers
counting up, by twos
Consecutive Primes
counting up, by primes
Evenly spaced sets
values of the numbers in a set go up or down by the same amount (increment)
Consecutive multiples
all of the values in a set are multiples of the increment
Counting consecutive integers
Last - First + 1
Counting consecutive multiples
((Last - First) / increment) + 1 (start Last and First should be multiples of the increment within the set before using this strategy)
Properties of Evenly Spaced Sets
1) Mean and Median are equal (doesn’t matter if odd or even number in set, just that equally spaced)
2) Mean and Median are equal to the average of the first and last terms (FIRST + LAST)/2
Sum of Consecutive Integers
((First+Last)/2) * (First -Last + 1)
