Statistics revision 1 Flashcards
What is statistics?
Method for organising, summarising, and interpreting data
Define population
The entire set of individuals
Define sample
Group selected from the population to study
Why use a sample?
As populations are very large making it impossible to study
What characteristic describes a sample?
Statistic
What characteristic describes a population?
parameter
What are sample statistics representative of?
the corresponding population
What is a sampling error?
Difference between a sample statistic and population parameter
Describe descriptive statistics
the method which organises, summarises and simplifies data
Describe inferential statistics
uses sample data to make inferences about a population
What is a variable?
a characteristic or condition that changes
Sample results are…
generalised to the corresponding population
What is the correlational method?
two variables observed to determine a relationship
What are the limitations of correlational methods?
Cannot explain cause and effect relationships.
Describe experimental methods
One variable is manipulated while observing another variable to establish cause and effect.
What is an independent variable?
Variable that is manipulated. Antecedent variable manipulated prior to observing dependent variable.
What is a dependent variable?
The variable observed to assess the affect of the treatment
What is the difference between the correlational method and the experimental method
Experimental method = one variable is measured
Correlational method = both variables are measured
Explain the control condition
Some participants received no treatment or a placebo/neutral treatment
purpose of control condition….
baseline for comparison
Describe the experimental condition
participants receive the experimental treatment
Explain the concept of control
The researcher exercises control so that extraneous or confounding variables do not influence the relaionship
What are confounding variables
variables you are not researching that may affect outcomes
types of confounding variables
Situational, participant, experimenter, and demand characteristics e.g conforming to test conditions, social desirability
What is random assignment?
Each participant has an equal chance of being assigned to either condition.
Purpose of random assignment
Distributes participant characteristics evenly, so that both groups do differ greatly in terms of gender, age, intelligence etc.
What are environmental variables?
time of day, light, dark, weather, hot, cold etc
What are participant variables?
age, gender, intelligence
What is a matching condition?
equivalent groups or environments e.g all groups have 40% females and 60% males.
Holding them constant means…
e.g researchers might only use 10 year old boys - thereby holding age and gender constant.
What is a construct?
internal attributes which can not be directly observed e.g Anxious, intelligence, hungry, sad
Operational definition is
Defining a concept or construct by the operations used to represent or measure it e.g intelligence measured by performance tests
What is a discrete variable?
has no intermediate values. e.g number of children, number on a dice, number of students present each day. Impossible to observe an intermediate value
What is a continuous variable?
An infinite number of possible values that fall between values. e.g height, weight, time.
What is the nominal scale?
Categorical - labels observations e.g race, gender, occupation
What is the ordinal scale?
Categories ordered by rank - such as 1st, 2nd, 3rd. Small, medium, large. Upper, middle, lower
What is an interval scale?
metric - ordered exactly the same e.g inch, cm, degree
What is a ratio scale?
metric - has a zero point that is not arbitrary e.g gallons with zero gallons being empty.
What is a mediating variable?
Explains how two variables are related
What is a moderating variable?
affects the strength and direction of that relationship
What is the mean?
is the sum of all scores divided by the number of all scores
The median is…
the central number or midpoint of the data set of scores
The mode is
the number that appears the most in the data set of scores
What is the standard deviation?
is a measure of how dispersed the data is in relation to the mean
What is the effect size?
Effect size is a quantitative measure of the magnitude of the experimental effect. The larger the effect size the stronger the relationship between two variables.
What is operationalism?
Representing constructs by a specific set of operations
