Stats midterm Flashcards
Population
set of all individuals in a particular study
Parameters
value that describes a population, usually derived from measurements of the individuals in the population
Sample
set of individuals selected to represent the population in a research study
Statistics
value that describes a sample, usually derived from measurements of the individuals in the sample
Variable
characteristic or condition that changes or has different values for different individuals
data
measurements or observations
data set
collection of measurements or observations
datum
single measurement or observation; commonly called a score or raw score
descriptive statistic
procedure used to summarize, organize, and simplify data
inferential statistic
technique that allows one to make generalizations about the populations from which samples were selected
sampling error
naturally occurring discrepancy between a sample statistic and the corresponding population parameter
construct
internal attribute that cannot be directly observed but is useful for describing and explaining behavior
operational definition
procedure for measuring external behavior wherein the resulting measurements measure a hypothetical construct
discrete variable
value consisting of separate, indivisible categories, wherein no values can exist between two neighboring categories
continuous varibale
value which is divisible into an infinite number of fractional parts
real limit
boundary of intervals for scores that are represented on a continuous number line
upper real limit
boundary at the top of the interval
lower real limit
boundary at the bottom on the interval
lower real limit
boundary at the bottom on the interval
nominal scale
set of categories that have different names
ordinal scale
set of categories that are organized in an ordered sequence
interval scale
set of ordered categories that are all intervals of exactly the same size
ratio scale
set of ordered categories wherein a zero score indicates none of the variable being measured
descriptive research
measuring separate variables with the intent of simply describing the individual variables
correlational method
observing two different variables to determine whether there is a relationship between them or not
experimental method
manipulating one variable while another variable is observed and measured
independent variable
value that is manipulated by the researcher
dependent variable
value that is observed to assess the effect of the treatment
control condition
group that either receives no treatment or receives a neutral, placebo treatment
experimental condition
group that receives the experimental treatment
nonequivalent groups study
score comparison method where the researcher does not control which participants go into which group
pre-post study
method of using the passage of time to create the groups of scores
quasi-independent variable
value that is used to create the different groups of scores
Symmetrical distributions
distribution in which one side is a mirror image of the other
skewed distributions - positive skew
distribution wherein the tail points towards the right end of the X-axis (–>)
skewed distributions - negative skew
distribution wherein the tail points towards the left end of the X-axis (
frequency distribution
organized tabulation showing number of individuals located in each category on the scale of measurement
grouped frequency distribution table
graph presenting group scores rather than individual values
class interval
group of scores in a grouped frequency distribution table
apparent limit
value that appears to form the upper and lower boundaries for the class interval
histogram
graph with a bar drawn above each score and with no space between adjacent bars
polygon
graph with a dot centered above each score according to the frequency of each score
bar graph
diagram with a rule drawn above each score with spaces left between adjacent bars
relative frequency
estimated number of occurrences of a score
skewed distribution
graph in which scores pile up towards one end of the scale and taper off
tail
distribution section where scores taper off toward one end of a distribution
mean
sum of the scores divided by the number of scores
population mean
formula where in all scores in the population are added, and then divided by N
sample mean
formula with symbols to signify population subset values
weighted mean
formula combining multiple sets of scores and dividing to find overall mean for combined group
central tendency
statistical measure to determine a single score that defines the midpoint of a distribution
median
midpoint in a list of scores listed in order from smallest to largest
mode
score or category that has the greatest frequency in a frequency distribution
bimodal
distribution with 2 scores with greatest frequency
multimodal
a distribution with more than 2 scores with greatest frequency
major mode
taller peak when two scores with greatest frequency have unequal frequencies
minor mode
shorter peak when two scores with greatest frequency have unequal frequencies
line graph
diagram used when values on a horizontal axis are measured on an interval scale or ratio scale
Steps of determining Standard Deviation and Variance
- determine mean - X/N
- determine deviation from mean - X - mew
- add deviation - sum of (X - mew) = 0 will always be zero
- calculate average of deviation scores - sum of (X - mew)^2/N this is the variance
- square root the variance this is the standard deviation
unbiased estimate of the population parameter
of the average value of the statistic , obtained over many different samples, is equal to the population parameters
biased estimate of the population parameter
systemically overestimates or underestimates the population parameter
raw score
original, unchanged datum that is the direct result of measurement
z-score
specification of the precise location of each X value within a distribution
z-score transformation
relabeling of X values in a population into precise X-value locations within in a distribution
standardized distribution
composition of data used to make dissimilar distributions comparable
standardized score
result from relabeling data into new table with positive, whole-number predetermined mean and standard deviation
probability
fraction or proportion of all the possible outcomes
random sampling
selection process wherein each individual in the population has an equal chance of being selected
single random sample
data set obtained using selection process wherein each individual has equal chance of being selected
independent random sample
data set obtained using selection process wherein the probability of being selected stays constant
independent random sampling
selection process wherein the probability of being selected stays constant from one selection to next
sampling with replacement
selection process that return individuals to the population in order to keep probabilities from changing
sample without replacement
selection process that does not require constant probabilities
unit normal table
list or proportions of the normal distribution for a full range of possible z-score values
percentile rank
portion of individuals in a distribution with scores less than/equal to the specific score
percentile
score referred to by its portion of scores less than/equal to the specific score
sampling error
natural discrepancy between a statistic and its corresponding population paramater
distribution of sample means
collection for all possible random data sets of a particular size
sampling distribution
statistics obtained by selecting all possible samples of a specific size from a population
central limit theorem
mathematical proposition which serves as a cornerstone for much of inferential statistics
expected value of M
mean of distribution of sample means which is always equal to the population mean
standard error of M
measure of distance expected between sample mean and population mean
law of large numbers
rule that larger sample size increases probability that sample and population means will be close
