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65 Cards in this Set
 Front
 Back
Definition
Descriptive Statistics 
Serves as a tool to describe or summarize or reduce to manageable form.


Definition
Quantitative 
Measures of height, weight, time, etc... Dealing with numbers


Definition
Qualitative 
Gender, college major, type of pet, etc...Dealing with descriptors


Definition
Inferential Statistics 
Purpose is to predict or estimate characteristics of a population from a knowledge of the characteristics of only a sample of the population


Definition
Population 
Any group of persons having a defined characteristic


Definition
Sample 
A portion of the population


Definition
Variable 
Any observation that can take different values (e.g. gender or race)


Definition
Attribute 
A specific value on a variable (e.g. female or male)


Definition
Measurement 
Transforms attributes into more tractable things, numbers.


What are the Measurement Scales

Nominal
Ordinal Interval Ratio 

Definition
Nominal Measurements 
lowest level of measurements
Grouping or categorizing with respect to some attribute/quality Anything that can be placed into a category Code with numbers 

Examples
Nominal 
College Major
ethnicity Gender Eye Color 

Definition
Ordinal Measurements 
RANKING
ranks an attribute a level above nominal possible with different amounts of an attribute 

Examples
Ordinal 
Class Ranking
Order of people crossing the finish line Rank of feeling on a scale 

Definition
Interval Measurement 
Describe the size/attribute of the differences amoung things
Zero= NOT correspond to absence of variable measured 

Examples
Interval 
Temperature
Calendar year 

Definition
Ratio Measurement 
Highest level of measurements
same as interval BUT zero=the absence of the property being measured 

Examples
Ratio 
Age
Height Weight distance Time 

Definition
Continuous Variable 
A variable that can assume an infinite number of whole and fractional values
e.g. weight, age, & reaction time 

Definition
Discrete Variable 
A variable where measurement can take on only separated values and can only assume whole numbers
e.g. number of children in the family 

Definition
Parametric Statistics 
Deals with the use of means and standard deviations and requires that the variables measured be of INTERVAL or RATIO data types


Definition
Nonparametric Statistics 
Deals with frequency counts or ranking of the measured variable
Requires that the measured variable be NOMINAL or ORDINAL 

Definition
Independent Variable 
"Grouping"
The experimental variable or the treatment variable. It is manipulated in some manner so it may be described in that manner 

Definition
Dependent Variable 
Used to describe the varibales being measured or the variable of interest (research/outcome variable)


Definition
Measures of Central Tendency 
Describe typical, average, or representative scores
Convey info about the center of a distribution of a set of scores Most widely used of all statistical descriptions of data 

What are the common types of measures of central tendency

Mode
Median Mean 

Definition
Mode 
The score or observation that occurs most frequently
appropriate for ANY variable and may be used with ALL data types (especially with nominal) 

Definition
Median 
The 50th percentile of a distribution. The midpoint of the distribution
equal number of observations above and below the median. You have to rank the scores in order (highlow, lowhigh, etc...) 

What can Percentile Rank be used for?

Often used for establishing things like obesity in growing children


Definition
Mean 
The arithmetic average of a set of numbers
every score in the distribution is used in calculating the mean. most widely used of the central tendency the foundation for statistical concepts 

Definition
Trimmed Mean 
A mean calculated with the lowest and highest scores discarded.


What are the 2 most important statistical characteristics of any distribution of scores

1)Central Tendency
2)Variablility 

What are the types of Variability

range
variance standard deviation 

Definition
Range 
The difference between the largest and smallest scores in a distribution (and only these two scores)
Problems: Outliers increase ranges & little to no value in inferential statistics 

Definition
deviation scores 
Reflect something about the degree of variation in a set of scores


Definition
Sum of Squares 
to square each deviation and then sum the squared deviation scores (instead of working with the absolute value of the deviation scores).


Definition
Variance 
The mean of the squared deviation scores divided by the degrees of freedom, also known as the MEAN SQUARE
Not very useful in descriptive measure 

Definition
Degrees of freedom 
Number in the sample minus one. represents the number of scores that are free to vary


Definition
Standard Deviation 
The square root of the variance.
Extensively used in descriptive statistics most commonly used measure of the variability of the scores 

What is a graph

A visual representation that are used to describe the characteristics of a distribution of scores


Definition
Rank Order Distribution 
A method where the scores are put in order from high to low


Definition
Simple Frequency Distribution 
a method where the frequency of scores at each value of the variable are listed
Works well when the range of the score is small 

Definition
Group Frequency Distribution 
a method where the frequency of scores are grouped into classes or intervals


If the range scores is large which distribution is best?

Grouped Fredquency Distribution


How many intervals is best in a data?

1020 intervals


If a range of scores is great how does it affect the intervals?

More intervals


What happens when info/data is put is grouped into intervals?

information loss.. fewer the intervals, the greater the loss


How many intervals?

this question is answered by some compromise b/n the importance of precision and the ease of the interpretation for the intended audience


Once you have a freq. distribution what is the best way to display that data?

in the form of a table


most common methods of graphing

histogram
frequency polygon ogive curve (cummulative freq. polygon) 

Frequency polygon is..

similar to a histogram but a line graph is used data is sometimes presented in the form of presentages


Cumulative Freq. Polygon

= Ogive curve
Principal value of this type of graph is that info is arranged in such a way the percentile rank of any observation can be easily estimated 

Types of distributions: Normal

symmetrical 50% on each side
 bell shaped mean, median, mode are equal if we know the mean & standard deviation, each individual's performance on the dependent variable can be evaluated numerous variables are normally distributed or approximately so (IQ scores, heightof adult women, etc.) 

Other types of distributions

bimodal
multomodal rectangular (no true mode) skewed distributions (positive/negative) 

Unimodal distribution

one mode as in the normal distribution
mean, median and mode = equal 

bimodal distriubtion

two modes in distribution


multimodal

three or more modes


in skewed distributions what happens to the mean?

positively skewed mean will be larger than the median or mode
Negatively skewed mean will be smaller than the median or mode 

In skewed distributions where is the median?

between mode and mean (usually closer to the mean)


What incr. as the magnitude of the skewdness increase?

degree of symmetry
differ among mena, median & mode 

Skewedness = ?

3(Mean Median)/standard devitaion


Kurtosis

measure of reltive peakedness in a curve


Platykuric

flat, broad


Leptokuric distribution

slender, narrow


what does degrees of freedome fix in a data set?

it corrects for sampling error
