Mean
Average; the sum total of a data set divided by the number of values in the set. Gives the average value of the entire set
Median
The middle value of a data set that is in numerical order. If the number of values is even you divide the middle two values.
Mode
The number that occurs most in a data set. If every number occurs the same amount of times there is no mode
Descriptive Statistics
Tabular, graphical, and numerical summaries of data."
Examples: Skewness, Average, Etc
Nominal Scale
The scale of measurement for a variable when the data are labels or names used to identify an attribute of an element. Nominal data may be non-numeric or numeric.
Ordinal Scale
The scale of measurement for a variable if the data exhibit the properties of nominal data and the order or rank of the data is meaningful. Ordinal data may be non-numeric or numeric.
Interval Scale
The Scale of measurement for a variable if the data demonstrate the properties of ordinal data and the internal between values is expressed in terms of a fixed unit of measure. Interval data are always numeric
Ratio Scale
The scale of measurement for a variable if the data demonstrate all the properties of interval data and the ratio of two values is meaningful. Ratio data are always numeric.
Categorical Data
Labels or names used to identify an attribute of each element. Categorical data use either the nominal or ordinal scale of measurement and may be non-numeric or numeric.
Quantitative Data
Numeric values that indicate how much or how many of something. Quantitative data are obtained using either the interval or ratio scale of measurement.
Statistical Inference
The process of using data obtained from a sample to make estimates or test hypotheses about the characteristics of a population
Variance
(S�) = ?(X-Xbar)�/n-1
Standard Deviation
s, or ? = ??(X-Xbar)�/n-1
IS A HIGH QUALITY MEASUREMENT. Uses all the numbers in the set and a "sophisticated formula".
Ogive
A graph of cumulative distribution
Histogram
A graphical presentation of a frequency distribution. Class internals are placed on the horizontal axis and the bars are all touching.
Frequency Distribution
A tabular summary of data showing the number (frequency) of data values in each of several non-overlapping classes.
Relative Frequency Distribution
A tabular summary of data showing the percentage of data values in each of several non-overlapping classes.
Measures of Dispersion
Examples: Skewness, Coefficient of Variation, Variance
Why use (n-1)?
- To remove constraint of ?(X-Xbar)
- Dividing by just N results in an underestimation with a sample when calculating population standard deviations.