Culture

Math, A Practical Art

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 – 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 – mean)2 / total frequencies]
  • Normal Distribution: z = (data value – 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  |  x2 |  xy, and sum of each column.    where ∑ = sum   n = # of points
    y = a + bx                  b = [n∑(xy) – (∑x)( ∑y)] / [n∑ (x2) – (∑x)2]                 a = [∑y – b(∑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: reff = (1 + r)n – 1              [r = periodic interest rate and n = number of periods per year)
  • To get rid of exponent: move n outside number, LN both side                 512n = 25 … 12n(ln5) = (ln25)
  • Annuity (fixed deposit) r = periodic rate    n = # of deposits
  • Amount in Annuity = PMT [ ((1+r)n – 1) / r]
  • Loans formula r = periodic rate    n = # of payments
  • Loan = PMT [(1- (1 + r) –n ) / r]
Standard