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