Exam 1 Flashcards
sample
the set of data you have access to in scientific study
random assignment
a required procedure in any experiment, in which the value of the independent variable assigned to each subject is determined purely by chance
Outlier
a member of a sample that is noticeably far from the rest of the distribution
variance
a measure of variability in a distribution, equal to the average swuared deviation from teh mean
mean
a measure of central tendency, defined ( when there are finitely many scores) as the sum of scores divided by the number of scores
operational definition
the procedure by which a construct is measure for a particular study
tail
either end of a distribution, containing the highest or lowest scores
quartile
a value of a variable that is greater than 1, 2, or 3 quarters of the scores in a distribution
standardized distribution
a distribution of z-scores; a distrubiton that has been transfromed to have a mean of 0 and a standard deviation of 1
what affects reliability?
sample size (increases reliability) variability (decreases reliability) effect size (increases reliability)
X
the variable we measure in a scientific study
n
the size of the sample
N
the size of the population
M
mean of the sample
mew greek letter mu
the mean of the population
x
any possible value of the measurement variable X
f(x)
the frequency of x, meaning the number of members of the population of sample for which X=x
P
probability; P(event) means the probability that event will occur. When x is a value in a populaiton, P(x) is the fraction of the population for which X=x, or the probability that if we select a member of the population at random, the value of X for that memeber willb e x
sigma
standard deviaton of the population
sigma squared
variance of population
variable
a characteristic or condition that canges or has different value for different individuals
data(plural)
measurements or observations
data set
a colletion of measurements or observations
parameter
a value that describes a population
descriptive statistics
statistical procedures used to summarize, organize or simplify data
inferential statistics
consists of techniques taht allow us to study samples and then make generalizations about the populations from which they were selected
sampling error
the discrepancy or amount of error, that exists between a smaple statistic and the corresponding population parameter
correlational method
two different variables are obsered to determine whether there is a relationship between them
experimental method
onee variable is manipulated while another variable is observed and measured. To establish a cause and effect relationship between the two variables, an experiment attempts to control all other varables to prevent them from influencing the results
independent variable
the variable that is manipulated by the researcher
dependent variable
the one that is observed to assess teh effect of the treatment
quasi-independent variable
the nonexperimental study, the “independent variable” that is used to create different groups o scores
control condiditon
do not recieve the experimental treatment
They recieve no treatment or placebo
operational definition
identifies a measurement procedure (a set of operations) for measuring an external behavior and uses the resulting measurements as a definition and a measurement of a hypothetical construct
real limits
the boundaries of interval for scores that are represented on a continous number line
upper real limit
the top of the interval
lower real limit
at the bottom of the interval
nominal scale
consists of a set of categories that have different names.
ordinal scale
consists of a set of categories that are organized in and ordered sequence. Measurements on an ordinal scale rank observations in terms of size or magnitude
ex: small, medium, large drinks
interval scale
consists of ordered categories that are all intervals of exactly the same size. Equal differences between numbers on scale reflect equal differences in magnitude. However, the zero point on an intervl scale is arbitrary and does not indicate a zero amount of the variable being measured
ratio scale
is an interval scale with the additional feature of an absolute zero point. With a ratio scale, ratios of numbers do not reflect ratios of numbers do reflect ratios of magnitude
frequency distribution
an organized tabulation of the number of individuals located in each category on the scale of measurement
symmetrical distrubiton
it is possible to draw a vertical line through the middle so that one side of the distribution is a mirror image of the other
skewed distribution
the scores tend to pile up toward one end of the scale and taper off gradually at the other end
tail
the section where the scores taper off toward one end of a distribution
percentile
a score is identified by its percentile rank
positively skewed
the tail points toward the positive (above zero) at the end of the x axis
negatively skewed
the tail points to the left,
central tendency
a statistical measure to determine a single score that defines the center of a distribution. The goal of central tendency is to fine the single score that is most typical or most representative of the entire group
median
the score that divides a distrubiton in half so that 50%of the individuals in a distribution have scores at or below the median
mode
the score or categoy that has the greatest frequency
range
is the distance from teh largest score to the smallest score in a distrubiton
interquartile range
the range covered by the middle 50% of the distribution
variablity
influences how easy it is to see patterns. In general, low variabilityy means that existing patterns can be seen clearly, whereas high variability tends to obsure any patterns that might exist
z-score
specifies the precise location of each X value within a distribution. the sign of the z-score(+ or =_ signifies whtether the score is above the mean (positive) or below the mean (negative)
raw score
unchanged scores that are a direct result of measurement
