# Statistics

 Statistics
 The art and science of collecting, interpreting, and analyzing data.
 Population
 A group of objects with common identifying characteristics; membership must be clearly defined.
 Statistic
 A property of a sample (example: X-bar)
 Parameter
 Characteristic or property of a population.
 Random Sampling Variation
 The uncertainty surrounding estimates of parameters (i.e. standard error of the mean).
 Consistent estimator
 As sample size increases, the accuracy of the statistic increases.
 Central Limit Theorem
 The shape of the sampling distribution becomes normally distributed as sample size increases regardless of the shape of the population distribution.
 Kurtosis
 ‘Peakedness’ of the curve or fourth moment around the mean of a population distribution.
 Nominal Data
 Classified by quality, not quantity (example: hair color, zodiac sign)
 Ratio-Scale Data
 Constant interval and a true zero point (example: weights, volumes).
 Interval-Scale Data
 Constant interval; zero point is arbitrary (example: C or F temperature).
 Ordinal Data
 Not equal units apart(example: places in a race).
 Compiler
 Software that translate a program from high level language to machine language and back again.
 Random Sample
 Each and every random set of data from a population has an equal and independent chance of being chosen.
 Analog Computer
 Data stored as strength of current.
 Digital Computer
 data stored as 1 or 0 (binary or machine language).
 Accuracy
 closeness to the truth.
 Precision
 Closeness of repeated measurements of the same object.
 Bias
 Pattern to the errors (always over or under estimate).
 Confounding Factor
 Variables that are not studied in an experiment yet can affect the response variables.
 Population Distribution
 A frequency distribution of some random variable (i.e. X) for the entire population.
 Sample Distribution
 A frequency distribution of some random variable (i.e. X) for a sample.
 Sampling Distribution
 A theoretical frequency distribution of some statistic (i.e. X-bar) for many samples of a given sample size from a population.
 Stratified Random Sample
 A population is broken into strata based on some variable and the sampling intensities are varied by the strata.
 Standard Error of the Mean
 The uncertainty of an estimation of a statistic of a given sample size.
 Mode
 Value or datum that occurs the most in the data set.
 Median
 Datum or value that divides an order data set exactly in half.
 Arithmetic Mean
 is the center of gravity of the frequency distribution.