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136 Cards in this Set

  • Front
  • Back
Alternative hypothesis
a research hypothesis
Bar chart
a graphic that displays how data fall into different categories or groups
Bell-shaped curve
symmetrical, single-peaked frequency distribution
Bias
the consistent underestimation or overestimation of a true value
Bimodal
curve with two equal scores of highest frequency
Binomial
even with only two possible outcomes
Bivariate
involving two variables
Box Plot
(box and whiskers) a graphic display of data indicating symmetry and central tendency
Central Limit Theorem
a rule that states that the smapling distribution of means from any population will be normal for a large sample n.
Central tendency
a statistical measure to determine a single score that defines the center of a distribution. The goal is to find the single score that is most typical or most representative of the entire group.
Chi-square
a probability distribution used to test the independence of two nominal variables
Class frequency
the number of observations that fall into each class interval
Class intervals
categories or groups contained in frequency graphics
Coefficient of determination
a measure of the proportion of wach other’s variability that two variables share
Confidence interval
the range of values that a population parameter could take at a given level of significance
Constant
characteristic or condition that does not vary but is the same for every individual
Constructs
internal attributes or characteristics that cannot be directly observed bt are useful for describing and explaining behavior
Continuous level
the probability of obtaining a given result by chance
Continuous variable
a variable that can be measured with whole numbers and fractional (or decimal) parts thereof
Control condition
do not receive experimental treatment. Instead, they receive no treatment or they receive a neutral, placebo treatment. Purpose of control condition is to probide baseline for comparison with the experimental condition.
Correlation coefficient
a measure of the degree to which two variables are linearly related
Correlational method
two variables are observed to determine whether there is a relationship between them
Critical value
the value of a computed statistic used as a threshold to decide whether the null hypothesis will be rejected
Data
Plural, measurements or observations; numerical information about variables
Datum
singular; single measurement or observation; commonly called score or raw score
Degrees of freedom
a parameter used to help select the critical value in som probability distributions
Dependent events
events such that the outcome of one has an effect on the probability of the outcome of the other
Dependent variable
a variable that is caused or influenced by another
Descriptive statistics
numerical data that describe phenomena
Directional test
a test of the prediction that one value is higher than another
Discrete variable
a variable that can be measured only by means of whole umbers
Disjoint occurrence
both outcomes unable to happen at the same time
Distribution
a collection of measurements; how scores tend to be dispersed about a measurement scale
Dot plot
a graphic that displays the variability in a small set of measures
Experimental method/condition
one 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 variables to prevent them from influencing the results
Frequency distribution
an organized tabulation of the number of individuals located in each category on the scale of measurement
Frequency histogram
a graphic that displays how many measures fall into different classes
Frequency polygon
a graphic presentation of frequency of a phenomenon that typically uses straight lines and points.
Grouped data
represented in a frequency table, formula for sample mean for grouped data xbar = Σfx n where f is frequency and x is midpoint
Grouped measures
a set of values that belong to the same class
Histogram
a graphic presentation of frequency of a phenomenon
Independent events
events such that the outcome of one has no effect on the probability of the outcome of the other
Independent variable
variable that is manipulated by the researcher. Usually consists of the two (or more) treatment conditions to which subjects are exposed; consists of the anteceent conditions that were manipulated prior to observing the dependent variable.
Inference
conclusion about the population parameter based upon analysis of a sample statistic
Inferential statistics
consists of techniques that allow us to study samples and then make generalizations about the populations from which they were selected
Intercept
the value of y at which a line crosses the vertical axis
Interquartile range
set of measures lying between the lower quartile (25th percentile) and the upper quartile (75th percentile), inclusive
Interval
a scale using numbers to rank order; its intervals are equal but with with an arbitrary 0 point
Interval scale
consists of ordered categories that are all intervals of exactly the same size. Equal differences between numbers on the scale reflect equal differences in magnitude. Ratios of magnitudes are not meaningful.
Joint occurrence
both outcomes happening simultaneously; P(AB)
Least squares
any line-or curve-fitting model that minimizes the squared distance of data points to the line
Lower quartile
(Q1), the 25th percentile of a set of measures
Mean
the sum of the measures in a distribution divided by the number of measures, x-(bar)= mean of sample, μ = mean of population, M= sample mean
Measures of central tendency
descriptive measures that indicate the center of a set of values
Median
the middle measure in an ordered distribution, for grouped data= median=L = w (.5n - Σfb)
w = interval width
n =
total number of measurements
w =
interval width
fmed =
frequency of the class containing the median
Σfb =
sum of the frequencies for all classes before the median class
Middle quartile
(Q2), the 50th percentile of a set of measures; the median
Mode
most frequent measure in a distribution
Mound-shaped curve
see bell-shaped curve
Mutually exclusive
evens such that the occurrence of one precludes the occurrence of the other
Negative relationship
a relationship between two variables such that when one increases, the other decreases
Nominal
a scale using numbers, symbols, or names to designate different subclasses
Non-directional test
a test of the prediction that two values are equal or a test that they are not equal
Non-parametric test
statistical test used when assumptions about normal distributions in the population cannot be met, or when the level of measurement is ordinal or less
Normal distribution
smooth bell-shaped curve symmetrical about the mean such that its shape and area obey the Empircal Rule
Null hypothesis
the reverse of the research hypothesis
Ogive
a graphic that displays a running total
Operational definition
identifies a measurement procedure(a set of operations), for measuring an external behavior and uses the resulting measurements as a definition and measurement of hypothical construct. Has two components= 1)describes a set of operations for measuring a construct; 2) defines the constructin terms of resulting measurements
One-tailed test
a test of the prediction that one value is higher than another
Order of Mathematical Operations
1) any calculation within parenthesis; 2) squaring (or raising to other exponents); 3) multiplying &/or dividing (L→R); 4) summation using the Σ notation; 5) any other addition or subtraction
Ordinal
A scale using numbers or symbols to rank order; its intervals are unspecified
Outlier
a data point that falls far from most other points; a score extremely divergent from the other measures of a set
Parameter
a characteristic of a population
Percentile
the value in an ordered set of measurements such that P% of the measures lie below that value
Percentile rank
the percentage of individuals in the distribution with scores at or below the particular value
Pie chart
a graphic that displays parts of the whole
Point estimate
a number computed from a sample to represent a population parameter
Population
a group of phenomena that have something in common
Positive relationship
a relationship between two variables such that when one increases, the other increases, or when one decreases, the other decreases
Power
the probability that a test will reject the null hypothesis when it is, in fact, false
Probability
a quantitative measure of the chances for a particular outcome or outcomes
Probability distribution
a smooth curve indicating the frequency distribution for a continuous random variable
Qualitative variable
phenomenon measured in kind, that is, non numerical units
Quasi-independent variable
research studies that involve comparing groups that are not created by manipulating an independent variable. Instead, the groups are usually determined by a participant variable, or a time variable (pre-,post).
Random error
error that occurs as a result of sampling variability
Rank
the percentage of individuals in the distribution with scores at or below the particular value
Range
difference between the largest and smallest measures of a set
Ratio
a scale using numbers to rank order; its intervals are equal, and the scale has an absolute 0 point
Ratio scale
interval scale with the additional feature of an absolute zero point. Ratios of numbers DO reflect ratios of magnitude
Region of acceptance
the area of a probability curve in which a computed test statistic will lead to acceptance of the null hypothesis
Region of rejection
the area of a probability curve in which a computed test statistic will lead to rejection of the null hypothesis
Regression
a statistical procedure used to estimate the linear dependence of one or more independent variables on a dependent variable
Relative frequency
the ratio of class frequency to total number of measures
Research hypothesis
a prediction or expectation to be tested
Residual
the vertical distance between a predicted value y and its actual value
Sample
a group of members of a population selected to represent the population
Sampling distribution
the distribution obtained by computing a statistic for a large number of samples drawn from the same population
Sampling error
the discrepancy, or amount of error, that exists between a sample statistic and the corresponding population parameter
Sampling variability
the tendency of the same statistic computed from a number of random samples drawn from the same population to differ
Scatterplot
a graphic display used to illustrate degree of correlation between two variables
Skewed
a distribution displaced at one end of the scale and a tail strung out at the other end
Slope
a measure of a line’s slant
Standard deviation
a measure of data variation; the square root of the variance
Standard deviation of a sample
s
Standard deviation of a population
σ
Standard error
a measure of the random variability of a statistic
Standardize
to convert to a z-score
Statistic
a characteristic of a sample
Statistical significance
the probability of obtaining a given result by chance
Statistics
a branch of mathematics that describes and reasons from numerical observations; or descriptive measures of a sample
Stem-and-leaf
graphic display that shows actual scores as well as distribution of classes
Symmetry
a shape such that one side is the exact mirror image of the other
Systematic error
the consistent underestimation or overestimation of a true value
t-distribution
a probability distribution often used when the population standard deviation is not known or when the sample size is small
tabled value
the value of a computed statistic used as a threshold to decide whether the null hypothesis will be rejected
test statistic
a computed quantity used to decide hypothesis tests
two-tailed test
a test of the prediction that two values are equal, or a test that they are not equal
type I error
rejecting the bull hypothesis that is, in fact, true
type II error
failing to reject a null hypothesis that is, in fact, false
upper quartile
(Q3), the 75th percentile of a set of measures
value
a measurement or classification of a variable
variable
an observable characteristic of a phenomenon that can be measured or classified
variance
a measure of data variation; the mean of the squared deviation scores about the means of a distribution
variance of a sample
s2
within treatment variability
scores differing from one another even within a single treatment group; researcher has to consider how to describe and characterize sets of scores before they can be compared
σ2
variance of the population
z-score
a unit of measurement obtained by subtracting the mean and dividing by the standard deviation
Σx
sum of measures
Σx2
sum of the squares of the measures