Reading 8: Statistical Concepts and Market Returns Flashcards
Descriptive Statistics
Are used to summarize important characteristics of a large data set
Inferential Statistics
Procedures used to make judgments about a larger data set based on the statistical characteristics of a smaller set (a sample)
Population
A set of all possible members of a stated group e.g. all stocks on NYSE
Sample
A subset of the population of interest
Types of Measurement Scales
Nominal
Ordinal
Interval
Ratio
Nominal Scales
Data put into categories that have no particular order (range with the least amount of information)
Ordinal Scales
Data is put into categories that can be ordered according to some characteristics
Reveals nothing about performance differences
(Higher level of measurement than nominal)
Interval Scale
Temperature
Relative ranking like ordinal with differences in data values being meaningful, however ratios, such as twice as much/large are not meaningful
Measurement of zero does not mean the absence of what we are measuring
Ratio Scale
Most refined level of measurement (Money)
Ratios of values (twice as much etc.) are meaningful, and zero measures the complete absence of the characteristics being measured
Parameter
Numerical measure used to describe a characteristic of a population
E.g. mean or standard deviation of returns
Sample Statistic
Characteristic of a Sample
Frequency Distribution
Groups observations into a classes or intervals. An interval is a range of values
Relative Frequency
The percentage of total observations that fall within each interval
Cumulative Relative Frequency
The sum of all relative frequencies up to and including the given interval
Histogram
Graphical presentation of absolute frequency distribution (Bar Chart)
Benefit: Allows us to see where most observations are concentrated
Frequency Polygon
Midpoint of each interval is plotted on the horizontal axis and the absolute frequency is plotted on the vertical axis (Line Chart)
Measures of Central Tendency
Used to identify the center or average of a data set. Can be used to represent the expected value of a dataset
Population Mean
Sum of all values in a population divided by the total number of observations in the population (only one possible mean)
Sample Mean
Sum of all values in a sample divided by the total number of observations in the sample (used to make inferences about the population)
Arithmetic Means (Properties)
- All interval and ratio data sets have an arithmetic mean
- All data values are considered and included
- Only one mean
- Sum of all deviations of each observation always equals zero
Arithmetic Mean (Negative)
Outliers can have a disproportionate effect
Arithmetic Mean (Positive)
Uses all information available from observations
Weighted Mean
Recognizes that outliers have a disproportionate effect
Used to calculate portfolio returns (weighted average return of the individual assets in the portfolio)