Formulas And Stuff Flashcards
Percentage change
Percent change = Actual change/original amount x 100
Mortgages formula
R = interest rate per period
P = starting balance of loan
N = number of payments in total
P [r(1+r)^n / (1+r)^n - 1]
Lower outliers
Q1 - 1.5 ( Q3 - Q1 )
Higher outliers
Q3 + 1.5 ( Q3 - Q1 )
Normal distribution notation
X ~ N ( mean, SD^2)
Z values equation
Z = x - u / o
x = point from mean
u = mean
o = standard deviation
Confidence intervals equation
x̄ +/- Z times o/square root of n
How much data is within 1 SD of the mean?
68%
How much data is within 2 SD of the mean?
95%
How much data is within 3 SD of the mean?
99.7%
Random Sampling
Where everyone / thing has an equal chance of being picked, unbiased
What is Stratified Sampling?
Where the sample from each sub section should be proportionate to the total number in that sub section
What is systematic sampling?
A method with a random sample, with a fixed periodic interval, is selected from a larger population
What is cluster sampling?
A method where you divide a population into clusters, such as schools, and then randomly select some of these clusters as your sample
What is Quota sampling?
A non-probability sampling method that relies on the non-random selection of a set number or proportion of units
