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Stats final
statistics and research methods
86
Psychology
Undergraduate 3
04/23/2010

Additional Psychology Flashcards

 


 

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Term
descriptive statistics
Definition
statistical procedures used to summarize and simplify data
Term
inferential statistics
Definition
consists of techniques that allow us to study samples and then make generalizations about a population
Term
discrete variable
Definition
consists of separate indivisible categories (no values can exist between two neighboring categories)
Term
continuous variable
Definition
there are an infinite number of possible values that fall between any two observed values; divisible into an infinite number of parts
Term
real limits
Definition
the boundaries of intervals for scores that are represented on a continuous line; real limit separating two values is located directly in the middle
Term
variable
Definition
a characteristic or condition that changes or has different values for different individuals
Term
nominal scale
Definition
consists of a set of categories that have different names and measurements label and categorize observations, but do not make any quantitative distinctions between observations
Term
ordinal scale
Definition
consists of a set of categories that are organized in an ordered sequence and measurements rank observations in terms of size or magnitude
Term
interval scale
Definition
consists of ordered categories that are all intervals of exactly the same size and equal distances on the scale reflect different magnitudes
Term
ratio scale
Definition
an interval scale with the additional feature of an absolute zero point and ratios of numbers reflect ratios of magnitude
Term
frequency distribution
Definition
an organized tabulation of the number of individuals located in each category on the scale of measurement
Term
grouped frequency distribution
Definition
groups the scores into around ten intervals
Term
histogram
Definition
like a bar graph but displays the real limits of values
Term
bar graph
Definition
leaves spaces between adjacent bars
Term
frequency polygon
Definition
places a dot for the frequency of each score and connects them with a line
Term
stem and leaf display
Definition
places all but the last digit on the left and puts the last digit on the right; provides a view of the frequency and gives you the scores
Term
normal distributions
Definition
are symmetrical with the most scores right in the middle
Term
positive and negative skew
Definition
positive skew: to the left
negative skew: to the right
Term
kurtosis
Definition
a measure of the "peakedness" of the distribution; higher kurtosis means that more of the variance is the result of extreme scores; normal distribution has kurtosis of zero
Term
mean
Definition
the sum of the scores divided by the number of scores
Term
What happens to the mean when you add or subtract a constant from each score?
Definition
the same constant is added or subtracted from the mean
Term
What happens to the mean when you multiply or divide every score by a constant?
Definition
the mean changes in the same way
Term
median
Definition
the score that divides the distribution in half; equivalent to the 50th percentile
Term
mode
Definition
the score or category that has the greatest frequency; can be bimodal or multimodal
Term
Which measure of central tendency would you use for extreme or skewed distributions?
Definition
the median
Term
Which measure of central tendency would you use for distributions with undetermined values?
Definition
the median
Term
Which measure of central tendency would you use for an open ended (no upper of lower limit for one of the categories) distribution?
Definition
the median
Term
What is the preferred measure of central tendency for ordinal data?
Definition
the median
Term
Which measure of central tendency is best for data from a nominal scale?
Definition
the mode
Term
Which measure of central tendency is best for discrete variables?
Definition
the mode
Term
Which measure of central tendency describes the shape of the distribution?
Definition
the mode
Term
variability
Definition
provides a quantitative measure of the degree to which scores in a distribution are spread out or clustered together
Term
range
Definition
the difference between the upper real limit of the largest (maximum) X value and the lower real limit of the smallest (minimum) X value
Term
interquartile range
Definition
the range covered by the middle 50% of the distribution
Term
semi-interquartile range
Definition
half of the interquartile range
Term
deviation
Definition
distance from the mean
Term
population variance
Definition
mean squared deviation (the mean of the squared deviation scores
Term
standard deviation
Definition
the square root of the variance
Term
Will adding a constant to each score change the distribution?
Definition
no
Term
What will multiplying each score by a constant do to the standard deviation?
Definition
it will cause it to be multiplied by the same constant
Term
unit normal distribution
Definition
the distribution of z-scores that a distribution can be transformed into
Term
percentile
Definition
a score when it is identified by its percentile rank
Term
percentile rank
Definition
the percentage of individuals int he distribution with scores at or below the particular value
Term
probability
Definition
a fraction or a proportion of all the possible outcomes
Term
sampling distribution of means
Definition
the collection of sample means for all the possible ransom sample of a particular size (n) that can be obtained from a population
Term
central limit theorem
Definition
for any population with mean and standard deviation, the distribution of sample means for sample means for sample size n will have a standard deviation of (u) and a standard deviation of (o/n^1/2) and will approach a normal distribution as n approaches infinity
Term
null hypothesis
Definition
states that there is no difference between sample mean and population mean
Term
alternative hypothesis
Definition
states that there is a significant difference between the sample and population means
Term
test statistic
Definition
indicates that the sample data are converted into a single, specific statistic that is used to test the hypothesis
Term
level of significance (alpha)
Definition
probability of a Type I error; a probability value that is used to define the very unlikely sample outcomes if the null hypothesis is true
Term
test statistic
Definition
indicates that the sample data are converted into a single, specific statistic that is used to test the hypothesis
Term
type II error
Definition
occurs when a researcher fails to reject a null hypothesis that is really false; means that the hypotheses test has failed to detect a real treatment effect
Term
critical region
Definition
composed of extreme sample values that are very unlikely to by obtained if the null hypothesis is true; boundaries determined by alpha level
Term
effect size
Definition
a measure of the strength of the relationship between two variables in a population or sample-based estimate of that quantity
Term
power
Definition
the probability that the test will correctly reject a false hypothesis (probability that the test will identify a treatment effect if one really exists)
Term
t statistic
Definition
used to test hypotheses about an unknown population mean when the standard deviation is unknown; formula has the same structure as the z-score formula, except that the t statistic uses the estimated standard error in the denominator
Term
degrees of freedom
Definition
describe the number of scores in a sample that are independent and free to vary
Term
independent variables
Definition
the variable that is manipulated by the researcher
Term
dependent variable
Definition
the variable that is observed in order to asses the effect of the treatment
Term
explained variance
Definition
measures the proportion to which a mathematical model account for the variation of the given data set
Term
point estimate
Definition
you use a single number as your estimate of an unknown quantity
Term
confidence interval
Definition
when an interval estimate is accompanied by a specific level of confidence (or probability)
Term
true experiment
Definition
subjects are randomly assigned to treatment conditions (levels of the independent variable); excellent for showing a cause/effect relationship
Term
quasi-experiment
Definition
measurement in the treatment level is determined by conditions beyond the control of the experimenter (subjects fall in pre-existing groups)
Term
correlational method
Definition
two variables are observed to determine whether there is a relationship between them
Term
Pearson correlation
Definition
measures the degree and direction of linear relationship between two variables
Term
operational definition
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
Term
What are the two components of an operational definition?
Definition
1) describes a set of operations for measuring a construct
2) defines the construct in terms of the resulting measurements
Term
probability sampling
Definition
any method of sampling that utilizes some form of random selection (have some process that assures different units in population have an equal chance of being selected)
Term
nonprobability sampling
Definition
subjects are not randomly selected
Term
confounding variables
Definition
an extraneous variable that correlates (positively or negatively) with both the IV and DV; control these factors to avoid a type I error
Term
experimenter bias
Definition
bias towards a result expected by the experimenter
Term
subject bias
Definition
the participant believes they know the purpose of the experiment and perform in a way that will support or discredit the experiment
Term
What are the advantages of the within-subjects design?
Definition
same group of subjects serves in more than one treatment;increases the power; reduces the error variance associated with individual differences
Term
What is the disadvantage of the within-subjects design?
Definition
carryover effects
Term
What are the two carryover effects?
Definition
practice and fatigue
Term
What is a between-subjects design?
Definition
use different subjects for each treatment condition
Term
What are the advantages of the between-subjects design?
Definition
sometimes the within-subjects design is improbable to use; no carryover effects
Term
What are the disadvantages of the between-subjects design?
Definition
scale of experiment can make it improbable to get the number of subjects necessary; individual differences can skew data; assignment bias (fail to assign random groups); environmental factors; generalization (cannot extrapolate the results to encompass wider groups)
Term
What is the difference between a positive and negative correlation?
Definition
In a positive correlation the two variables tend to move in the same direction, while in a negative correlation the two variables tend to move in opposite directions
Term
regression
Definition
the statistical technique for finding the best-fitting straight line for a set of data
Term
What is a multiple regression used for?
Definition
it is used to asses which of the possible independent variables is mainly responsible for the change in the dependent variable
Term
parametric tests
Definition
tests that concern parameters and require assumptions about parameters (t-test, anova, etc)
Term
nonparametric tests
Definition
do not have homogeneity of variance or a normal distribution (e.g. Chi-square test)
Term
Chi-square test
Definition
uses sample data to test hypotheses about the shape or proportions of a population distribution; determines how well the obtained sample proportions fit the population proportions specified by the null hypothesis
Term
envelope
Definition
encloses the data in a correlation graph; shows the shape and trend in the distribution
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