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Statistics for Psychology: Chapter 1
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Terms in this set (86)
Statistics
a branch of mathematics that focuses on the organization, analysis, and interpretation of a group of numbers
Descriptive statistics
procedures for summarizing a group of scores or otherwise making them more comprehensible
Inferential statistics
procedures for drawing conclusions based on the scores collected in a research study but going beyond them
variable
characteristic that can have different values
values
possible number or category that a score can have
score
particular person's value on a variable
numeric variable
variable whose values are numbers
equal-interval variable
variable in which the numbers stand for approximately equal amounts of what is being measured
ration scale
an equal-interval variable is measured on a ratio scale if it has an absolute zero point, meaning that the value of zero on the variable indicates a complete absence of the variable
discrete variable
variable that has specific values and that cannot have values between these specific values
continous variable
variable for which, in theory there are an infinite number of values between any two values
rank-order variable
numeric variable in which, in theory, there are an infinite number of values between any two values
nominal variable
variable with values that are categories
levels of measurement
types of underlying numerical information provided by a measure, such as equal interval, rank-order and nominal
frequency table
listing of number of individuals having each of the different values for a particualr variable
interval
range of values in a grouped frequency table that are grouped together
grouped frequency table
frequency table in which the number of individuals is given for each interval of values
histogram
barlike grap of a frequency distribution in which the values are plotted along teh horizontal axis and the height of each bar is the frequency of that value; the bars are usually placed next to each other without spaces
frequency distribution
pattern of frequencis over the various values; what a frequency table,histogram or frequency polygon describes
unimodal distribution
frequency distribution with one value having a larger frequency than any other
bimodal distribution
frequency distribution with two approximately equal frequencies, each clearly larger than any of the others
multimodal distribution
frequency distribution with two or more high frequencies separated by a lower frequency
rectangular distribution
frequency distribution in which all values have the same frequency roughly
symmetrical distribution
distribution in which the pattern of frequences on the left and right side are mirror images or each other
skewed distribution
distribution in which the scores pile up on one side of the middle and are spread out on the other side; not symmetrical
floor effect
situation in which many scores pile up at the low end of a distribution because it is not possible to have any lower score
ceiling effect
situation in which many scores pile up at the high end of a distribution because it is not possible to have a higher score
normal curve
specific, mathematically defined, bell shaped frequency distribution
kurtosis
extent to which a frequency distribution deviates from a normal curve in terms of whether its curve in teh middle is more peaked or flat than the normal curve
central tendency
typical or most representative value of a group of scores: mean, mode and median
mean
arithmetic average of a group of scores; sum of scores divided by the number of scores; "balancing point for the distribution of scores"
mode
the value with the greatest frequency in a distribution
median
middle score when all the scores in a distribution are arranged from lowest ot highest
outlier
score with an extreme value (very high or very low) in relation to the other scores in the distribution
variance
measure of how spread out a set of scores are; average of the squared deviations from the mean
deviation score
score minus the mean
squared deviation score
square of the difference between a score and the mean
sum of squared deviations
total of all the scores of each score's squared difference from the mean
standard deviation
square root of the average of squared deviations from the mean; the most common descriptive statistic for variation; approximately the average amount that scores in a distribution vary from the mean
computational formula
equation mathematically equivalent to the definitional formulal. Easier to use for figuring by hand
definitional formula
equation for a statistical procedure directly showing the meaning of the procedure
field research
a variety of research methods, ranging from low to high constraint
naturalistic observation
observation of events at they occur in natural settings
archival research
studying information from existing records made in natural settings
surveys
asking direct questions of people in natural settings
case studies
making extensive observations of an individual or small group of individuals
program evalution
conduction evalutations of applied procedures in natural settings
field experiments
conducting experiments in natural settings in order to understand causal relationships among variables
measurement reactivity
refers to the phenomenon of participants behaving differently than they might normally because they know that they are being nobserved
unobstrusive measures
measures of behavior that are not obvious to the person being observed and are less likely to influence the person's behavior
content analysis
involves examining records and identifying categories of events; which can be useful in archival research
representativeness
refers to how closely a sample resembles the population under study
causal inferences
conclusions that one or more variables brought about the observed state of another variable
ex posto fallacy
occurs when we draw unwarranted causal conclusions from the observation of contingent relationship
experimenter reactivity
any action by researchers that tends to influence the response of participants
experimenter bias
any impact that the researcher's expectations might have on the observations or recording of those observations
z score
number of standard deviations that a score is above (or below) the mean of its distribution; it is thus an ordinary score transformed so that it better describes the score's location in a distribution
normal distribution
frequency distribution that follows a normal curve
normal curve
specific, mathematically defined, bell-shaped frequency distribution that is symmetrical and unimodal; distributions observed in nature an in research commonly approximate it
random selection
method for selecting a sample that uses truly random procedures (usually meaning that each person in the population has an equal chance of being selected
population parameter
actual value of the mean, standard deviation and so on for populations
sample statistics
descriptive statistic, such as the mean or standard deviation, figured from the scores in a group of people studied
long-run relative frequency interpretation of probability
understanding of probability as the proportion of a particular outcome that you would get if the experiment were repeated many times
subjectuve interpretation of probability
way of understanding probability as the degree of one's certainty taht a particular outcome will occur
heuristic influence
occurs when theories or research findings generate interest, including disbelief and suggest further research questions
systematic influence
occurs when theories or research provide testable propositions for further research
behavioral variable
any observable response of an organism
stimulus variable
environmental factors that have actual or potential effects on an organism's repsonses
organismic variable
a characteristic of an organism that can be used to classify the organism for research purposes
manipulated independent variables
those that the experimenter actively controls
nonmanipulated independent variables
researchers assign participants to groups based on preexisting characteristics
hypothesis testing
procedure for deciding whether the outcome of a study supports a particular theory or practical innovation
differential research
compares two or more groups that differ on preexisting variables
cross sectional design
development psychologists compare groups of participants at different ages on some set of varaibles
cohort effect
shared life experiences of people of a given age and in a given culture may lead them to behave similarly
time-series designs
similar to longitudinal designs but involve multiple measurements taken before and after a manipulation
confounded
if two variables vary at the same time
artifacts
the result of confounding
experimenter expectancy
the tendency of investigators to see what they expect to see
filler items
not meant to meaure anything but rather draw the participants attention away form the real purpose of the measure
moderator variable
a variable that seems to modify the relationship between other variables
the coefficient of determination
the square root of the correlation, which shows the proportion of variance accounted for in a correlation
reliabilty
A measure that provides consistent measurement, regardless of whether it is measuring the intended construct,
validity
is the extent to which a concept, conclusion or measurement is well-founded and corresponds accurately to the real world
internal validity
The degree to which a study's independent variable caused differences in the study's dependent variable
external validity
the extent to which the results of a study can be generalized to other situations and to other people
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