## My Math Cheat Sheet

**Frequency**: the number of data values in a class**Relative**: frequencies divided by total data values**Percentage**: relative x 100**Frequency polygon:**line graph; pie chart**Mean:**sum of all values / total # of values OR for each (add) freq(value) / total freq of values**Median:**the middle number of the set, or split diff**Mode**: occurs most frequent, only bi-modal or no mode**Range:**subtract the lowest from highest in data set**Standard Deviation**: the sq. root of [{for each} (data value â€“ mean)^{2}/ number of data values**Draw the bell curve.**Make sure to account for the other half in the answer (50% above or below)**Std Dev. Grouped**: the sq. root of [{for each} freq (midpoint â€“ mean)^{2}/ total frequencies]**Normal Distribution:**z = (data value â€“ mean) / standard deviation**Margin of Error**: Margin = z value / 2 (sq. root of population) [confidence/2 then look up area.]**Regression Line:**Table of values:**x | y | x**, and sum of each column. where âˆ‘ = sum n = # of points^{2}| xy

y = a + bx b = [nâˆ‘(xy) â€“ (âˆ‘x)( âˆ‘y)] / [nâˆ‘ (x^{2}) â€“ (âˆ‘x)^{2}] a = [âˆ‘y â€“ b(âˆ‘x)] / n**Percent:**out of 100**Percent to Decimal:**Move decimal 2 & drop %**Fraction**<->**Decimal**key**Retail:**Price + Markup**% Inc or Dec:**amount of inc or decrease / base starting amt (use the inverse of the percent if needed)**Simple Interest rate**: I = Prt (principal x rate x time)**Amount Simple Int. Acct:**A = P(1 + rt)**Compound/Nominal rate:**A = P(1+r)^{n}[r = periodic interest rate = (annual rate / periods per yr)**and**n= number of time periods = (years x periods per yr)]**Compound interest over time.**Calculate each period. Then add all.

*Make sure n & r are correct!**Make sure time is all in the same units (years vs. months)!***Don’t remove negative w/1.****Effective Interest Rate**: r_{eff}= (1 + r)^{n}â€“ 1 [r = periodic interest rate**and**n = number of periods per year)**To get rid of exponent:**move n outside number, LN both side 5^{12n}= 25 â€¦ 12n(ln5) = (ln25)**Annuity**(fixed deposit)**Amount in****Annuity**= PMT [ ((1+r)^{n}â€“ 1) / r]**Loans formula**r = periodic rate n = # of payments**Loan**= PMT [(1- (1 + r)^{â€“n}) / r]