Statistics Definition of Statistics Statistics – Numerical Data Statistics – A Body of Theory and Methods Applied to Data to Aid in Decision-Making

Areas of Statistics Descriptive Statistics Probability Inferential Statistics

Summation Notation Observations: X1 X2 X3 X4 …. Xn Sum of Observations: ∑Xi = X1 + X2 + X3 + X4 …. + Xn Sum of Squared Observations: ∑Xi2 = X12 + X22 + X32 + X42 …. + Xn2 Rules for Summations: ( c – Constant) ∑c = n•c Special Case: ∑1 = n 2) ∑c•Xi = c•∑Xi 3) ∑(Xi + Yi) = ∑Xi + ∑Yi

Population vs Sample Population – A collection of all observations of a characteristic of interest Sample – A portion of a population Parameter – a measure of a population (µ,σ) Statistic – a measure of a sample (X,s)

Data Types Nominal Data – Descriptive Titles with no natural order. Ordinal Data – Data with a natural order but no distance measure Interval Data – Data with distance measure but no true zero Ratio Data – Data with a true zero.

Example Employee Ms Abba . . . . . . . . . . . . Mr Zee Sex F M Marital S M Age 32 46 Salary 63,000 51,000 Job Manager Foreman Tenure 8 25

Two Major Data Classifications Qualitative Data – Non-Metric Nominal Ordinal Quantitative Data – Metric Interval Ratio