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Psyc 210 Exam 1
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Gravity
Terms in this set (44)
descriptive statistics
describe large amounts of data in a single number or a few numbers
inferential statistics
make an intelligent guess about the population
sample
a set of observations drawn from the population of interest
population
includes all possible observations about which we'd like to know something
variables
observations of physical, attitudinal, and behavioral characteristics that can take on different values
discrete observations
can take on only specific values (whole #s) no other values can exist between these numbers
continuous observations
can take on a full range on values; an infinite number of potential values exist
nominal variables
used for observations that have categories or names as their values (categorizing males as "1" and females as "2")
ordinal variables
used for observations that have rankings (1st, 2nd, 3rd) as their values
interval variables
used for observations that have numbers as their values; the distance between 2 pairs of consecutive numbers is assumed to be equal
ratio variables
variables that meet the criteria for interval variables but also have meaningful zero points (ex: time running out in a game)
independent variable
has at least 2 levels that we either manipulate or observe to determine its effects on the dependent variable (ex: whether gender predicts attitude)
dependent variable
is the outcome variable that we hypothesize to be related to, or caused by, changes in the independent variable (ex: attitudes, what we measure)
confounding variable
any variable that systematically varies with the independent variable so that we cannot logically determine which variable is at work (losing weight, working out & taking diet pills, can't tell which one is responsible for weight loss. hypothesize that diet pills lead to weight loss, the exercise is confounding variable)
reliable measure
measure is one that is consistent
valid
one that measures what it was intended to measure
operational definition
specifies the operations or procedures used to measure or manipulate a variable
correlation
an association between 2 or more variables
random assignment
every participant in the study has on equal chance of being assigned to any of the groups, or experimental conditions in the study
experiment
a study in which participants are randomly assigned to a condition or level of one of more independent variables
between-group research design
an experiment in which all participants in the study experience one and only one level of the independent variable
within-groups research design
an experiment in which all participants experience the different levels of the independent variable
raw scores
data that have not yet been transformed or analyzed
frequency distribution
describes the pattern of a set of numbers by displaying a count or proportion for each possible value of a variable
frequency table
a visual depiction of data that shows how often each value occurred; that is, how many scores were at each value
grouped frequency table
allows us to depict data visually by reporting the frequencies within a given interval rather than the frequencies for a specific value
frequency polygon
a line graph, with the x-axis representing values (or midpoints of intervals) and the y-axis representing frequencies; a dot is placed at the frequency for each value (or midpoint) and the dots are connectedu
normal distribution
a specific frequency distribution that is a bell-shaped, symmetric, unimodal curve
skewed distribution
are distributions in which one of the tails of the distribution is pulled away from the center
positively skewed
the tail of the distribution extends to the right, in a positive direction
negatively skewed
data, which have a distribution with a tail that extends to the left, in a negative direction
floor effect
a situation in which a constraint prevents a variable from taking values below a certain point (giving MIT students a 5th grade math test)
ceiling effect
a situation in which a constraint prevents a variable from taking on values above a certain number (giving 5th graders an MIT test)
distribution
pattern of a set of numbers
bar graph
visual depiction of data in which the IV is nominal or ordinal and the DV is scale
central tendency
the descriptive statistic that best represents the center of a data set, the particular value that all the other data seem to be gathering around (mean, median, mode)
parameters
numbers based on whole populations
statistics
the numbers based on samples from a population
variance
the number of squared deviations from the mean
standard deviation
the square root of the average of the squared deviations from the mean, or the square root of variance
correlation coefficient
a statistic that quantifies a relation between 2 variables
positive correlation
an association between 2 variables such that participants with high scores on one variable tend to have high scores on the other variable as well, and those with low scores on one variable tend to have low scores on the other variable
negative correlation
an association between 2 variables in which participants with high scores on one variable tend to have low scores on the other variable
Pearson correlation coefficient
a statistic that quantifies a linear relation between 2 scale variables
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