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65 Cards in this Set

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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 (high-low, low-high, 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?
10-20 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