Term
| Alpha (Level of Significance) |
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Definition
| Refers to the probability of rejecting the null hypothesis when it is true: i.e., the probably of making a type 1 error. The value of alpha is set by an experimenter prior to collecting or analyzing the data. In psychological research, alpha is commonly set at either .01 or .05 |
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Term
| ANCOVA (Analysis of Covariance0 |
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Definition
| A version of ANOVA used to increase efficiency of the analysis by statistically removing variability in the DV that is due to an extraneous variable. When using the ANCOVA, each person's score on the DV is adjusted on the basis of his or her score on the extraneous variable. |
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Term
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Definition
| A disadvantage of the time-series and other within-subjects designs is that the analysis of the data can be confounded by autocorrelation, which occurs when subjects' performance on the post-test is likely to be correlated with their performance on the pretests. Autocorrelation can inflate the value of the inferential statistic (e.g., the t or F), there by resulting in an inreased probability of making a Type 1 error. |
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Term
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Definition
| Studies in which the effects of the different levels of one or more IVs are compared by administering each level or combination of levels to a different group of participants. |
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Term
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Definition
| Derived from the probability theory that predicts that the sampling distribution of the mean (1) will approach a normal shape as the sample size increases, regardless of the shape of the population distribution of scores; (2) has a mean equal to the population mean; and (3) has a standard deviation equal to the population standard deviation divided by the square root of the sample size. |
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Term
| Chi-Square Test / Single-Sample and Multiple Sample |
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Definition
| Inferential statistical tests used when the data to be analyzed represent a nominal scale. The single-sample chi-square test is used when the study includes one variable; the multiple-sample chi-square test when it includes two more more variables. |
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Term
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Definition
| In contrast to other forms of sampling (which involve selecting individuals from the population), cluster sampling entails selecting units or groups (clusters) of individuals from the population (e.g., schools, hospitals, clinics). |
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Term
| Correlation Coefficient /Pearson r, Point Biserial, Biserial, Eta |
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Definition
| The correlation coefficient is a numerical index of the relationship (degree of association) between two or more variables. The magnitude of the coefficient indicates the strength of the relationship; its sign indicates the direction (positive or negative). The Pearson r is used when data on both variables represent a continuous scale. The point biserial when one variable is a true dichotomy and the other is continuous. The biserial when one variable is an artificial dichotomoy and the other is continuous. Eta is when the variables are continuous by have a nonlinear relationship. |
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Term
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Definition
| A research design used to control carryover (order) effects. Involves administering the different levels of the IV to different subjects or groups of subjects in a different order. The Latin square design is a type of counterbalanced design. |
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Term
| Cross-Validation Shrinkage |
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Definition
| Refers to validating a correlation coefficient (e.g., a criterion-related validity coefficient on a new sample. Because the same chance factors operating in the original sample are not operating in the subsequent sample, the correlatio coefficient tends to "shrink" on cross-validation. In terms of the multiple correlation coefficient (R), shrinkage is greatest when the original sample is small and the number of predictors is large. |
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Term
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Definition
| Cues in the experimental situation that inform reserach participants of how they are expected to behavre during the course of study. Demand Characteristics can threaten a study's internal and external validity. |
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Term
| Discriminant Function Analysis |
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Definition
| The multivariate technique used when there are two or more continuous predictors and one discrete (nominal) criterion. Referred to as multiple discriminant function analysis when the criterion has more than two categories. |
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Term
| Experimental Research / True and Quasi-experimental |
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Definition
| Experimental Research involves conducting a study to test hypotheses about the relationships between independent and dependent variables. A true experimental study permits greater control over the experimental situation - its "hallmark" is random assignment to groups. A quasi-experimental permits less control. |
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Term
| Experimentwise Error Rate |
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Definition
| Refres to the probability of making a Type 1 error. As the number of statistical comparisons in a study increases, the experimentwise error rate also increases. |
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Term
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Definition
| The degree to which a study's results can be generalized to other people, settings, conditions, etc. |
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Term
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Definition
| The type of ANOVA used when a study includes tw oor more IV's (i.e., when the study has used a factorial design). Also referred to as a two-way ANOVA, three-way ANOVA, etc, with the words "two" and "three" referring to the number of IVs |
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Term
| Independent and Dependent Variables |
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Definition
| The independent (experimental) variable is manipulated in a research study for the purpose of determining its effects on the dependent variable - the variable that is believed to have an effect on the dependent variable. Each independent variable in a study must always have at least two levels. The dependent variable is observed and measured in a study and is believed to be affected by the indpendent variable. |
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Term
| Internal Validity / Maturation, History, Selection |
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Definition
| The degree to which a research study allows an investigator to conclude that observed variability in a dependent variable is due to the independent variable rather to to other factors. Maturation is one threat to internal validity. It occurs when a physical or psychological process or even occurs as the result of the passage of time, (e.g., increasing fatigure, decreasing motivation) and has systematic effect on subjects status on the dependent variable. Another potential threat is history, which refers to an event that is external to a research study and that is not relevant to the research hypothesis but that affects subjects' performance on the dependent variable in a systematic way and thereby confounds the results of the study. Selection threatens internal validity when participants in different traetment groups are initially different and, therefore, would differ at the end of the study even if no treatment had been applied. Selection is a threay when participants are not randomly assigned to groups. |
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Term
| Interval Recording/Event Sampling |
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Definition
| Interval recording is a method of behavioral sampling that involves dividing a period of time into discrete intervals and recording whether the behavior occurs in each interval. It is particularly useful for behaviors that have no clear beginning or end. Event sampling is a method of behavioral sampling that is useful for behaviors that are rare or that leave a permanent product. It involves recording each occurrence of a behavior during a predefined or preselected event. |
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Term
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Definition
| A causal (structural equation) modeling technique used to verify a predefined causal model or theory. More comples than path analysis, it allows two-way (non-recursive) paths and takes into account observed variables, the latent traits they are believed to measure, and the effects of measurement error. |
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Term
MANOVA (Mutlivariate Analysis of Variance)
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Definition
| A form of ANOVA used when a study includes one or more IVs and two or mroe DVs, each of which is measured on an interval or ratio scale. Use of the MANOVA helps reduce the experimentwise error rate and increases power by analyzing the effects of the IV(s) and on al DVs (simultaneously) |
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Term
| Measures of Central Tendency |
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Definition
mean, median, mode
You know these. |
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Term
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Definition
| Research designs in which both between-groups and within-subjects comparisons can be made. |
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Term
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Definition
| The multivariate technique used for predicting a score on a continuous criterion based on performance on two or more continuous and/or discrete predictors. Ideally, predictors included in a multiple regression equation will have low correlations with each other and high correlations with the criterion. (High correlations between predictors is referred to as "multicollinearity") The output of multiple regression is the multiple correlation coefficient and a multiple regression equation. |
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Term
| Normal Curve / Area under the normal curve |
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Definition
| A symmetrical bell-shaped distribution that is defined by a specific mathematical formula. When scores on a variable are normally-distributed, it is possible to conclude that a specific number of observations fall within certain areas of that distribution that are defined by the standard deviation: In a normal distribution, about 68% of observations fall between the scores that are plus or minus one standard deviation from the mean, 95% between the scores that are plus and minus two SDs from the mean, and 99% between the scores that are plus and minus 3 SDs from the mean. |
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Term
| Null and Alternative Hypotheses |
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Definition
| In experimental research, the investigator tests a verbal research hypothesis by simultaneously testing two competing hypotheses. The first of these, the null hypothesis, is stated in a way that implies that the independent variable does not have an effect on the dependent variable. The second statistical hypothesis, the alternative hypothesis, states the opposite of the null hypothesis. It is expressed in a way that implies that the IV does have an effect on the DV. |
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Term
| Parametric and Nonparametric Tests |
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Definition
Parametric tests are inferential statistical tests that are used when the data to be analyzed represent an intervial or a ratio scale and when certain assumptions about the population distribution(s) have been met: i.e., when scores on the variable of interest are normally distributed and when there is homoscedasticity (population variances are equal). An advantage of the parametric tests is that they are more "powerful" than the nonparametric tests.
Non parametric tests are inferential statistical tests used when the data to be analyzed represent either an ordinal or nominal scale or when the assumptions for a parametric test have not been met. Include the chi-square tests, the Mann-Whitney U, and the Wilcoxon matched-pairs test. |
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Term
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Definition
| A causal modeling technique used to verify a pre-defined causal model or theory. Involves translating the theory into a path diagram, collecting data on the variables of interest (the observed variables), and calculating and interpreting path coefficients. |
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Term
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Definition
| Technique used by cognitive psychologists to identify the cognitions underlying problem-solving and decision-making. Involves having an individual "think aloud" while working and then analyzing the record (protocol) of the individual's verbalizations. |
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Term
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Definition
| Refers to a method of assigning subjects to treatment groups using a random method - sometimes referred to as "randomization". Considered the "hallmark" of true experimental research because it enables an investigator to conclude that any observed effect of an IV is due to the IV rather than to error. (Not to be confused with random selection/sampling) |
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Term
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Definition
| Error that is unpredictable (random). Sampling error is a type of random error. |
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Term
| Randomized Block Factorial ANOVA |
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Definition
| A version of the ANOVA that is appropriate when blocking has been used as a method for controlling an extraneous variable. Allows an investigator to statistically analyze the main and interaction effects of the extraneous variable (which is being treated as an additional IV) |
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Term
| Rejection and Retention Regions |
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Definition
The rejection region of a sampling distribution contains those sample values (e.g., means) that are unlikely to be obtained simply as the result of sampling error. When an inferential statistical test indicates that the obtained sample value falls in the rejection region, the null hypothesis is rejected an the alternative hypothesis is retained. The size of the rejection region is defined by alpha.
The retention region is the region of the sampling distribtion that contains those values that are likely to be obatined simply as the result of sampling error. When an inferential statistical test indicates that an obtained sample value is in the retention region, the null hypothesis is retained an the alternative hypothesis is rejected. The retention region is equal to one minus alpha. |
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Term
| Sampling distribution of the mean / standard error of the means |
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Definition
| The distribution of sample means that would be obtained if an infinite number of equal-size samples were randomly selected from the population and the mean for each sample calcuated. The sampling distribution is normally-shaped, its mean equal to the population mean, and its standard deviation (the standard error of the means) is equal to the population standard deviation divided by the square root of the sample size. Used in inferential statistics to determin how likely it is to obtain a particular sample mean given the population mean, the population standard deviation, the sample size, and the level of significance. |
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Term
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Definition
| A method of categorizing the various ways to measure variables. Nominal, ordinal, interval, and ratio. |
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Term
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Definition
| A correlation coefficient can be squared to obtain a measure of shared variability. For example, if the correlation between X and Y is .50, this means that 25% of variability in Y is shared with (or is accounted for by) the variability in X. |
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Term
| Single-Subject Resigns / AB, Reversal, Multiple Baseline |
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Definition
| Single-subject designs all contain at least one A (baseline) and one B (treatment) phase and include multiple measures of the DV at regular intervals during each phase. The reversal design includes, at a minimum, two baseline phases and one treatment phase (e.h., and ABA or ABAB design). The treatment is withdrawn ("reversed") during the second and subsequent baseline phases. Use of the multiple-baseline design involves sequentially applying a treatment to different "baselines" (e.g., to different behaviors, settings, or subjects). |
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Term
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Definition
| Asymmetrical distributions in which the majority of scores are located on one side of the distribution. In a postively skewed distribution, most scores are in the low side but a few scores are in the high (positive) side of the distribution. In a negatively skewed distribution, the majority of the scores are in the high side of the distribution, but a few are in the low (negative) side. (Remember, it's the "tail that tells the tale"!) |
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Term
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Definition
| A measure of dispersion (variability) of scores around the mean of the distribution. Calculated by dividing the sum of the squared deviatio scores by N (or N-1) and taking the square root of the result. The square root of the variance. |
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Term
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Definition
| Poper refers to the probability of rejecting a false null hypothesis. Power cannot be directly controlled but can be increased by including a large sample, maximizing the effects of the IV, increasing the size of alpha, and reducing error. |
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Term
| Systematic Error / Extraneous Variables |
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Definition
| Systematic error is predictable error. Extraneous (confounding) variables are a source of systematic error. |
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Term
| T-tests / Single sample, Independent Samples, and Correlated Samples |
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Definition
| Parametic test used to compare two means. The single-sample t-test is used to compare a single obtained mean to a known or hypothesized population mean. The t-test for independent samples is used to compare means from two independent samples. The t-test for correlated samples is used to compare two sample means when subjects in teh two groups are related in some way (e.g., because they were matched on an extraneous variable or because a single-group pretest/posttest design was used) |
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Term
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Definition
| A type of analysis of variance used to assess linear and nonlinear trends with the independent variable is quantitative |
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Term
| Type I and Type II errors |
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Definition
Type I = occurs when a true null hypothesis is rejected. The probability of making a Type 1 error is equal to alpha.
Type II = occurs when a false null hypothesis is retained. The probability of making a Type II error is equal to beta (which is usually unknown) |
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Term
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Definition
| An experimental design in which each participant receives, at different times, each level of the IV (or combinations of the IVs) so that comparisions on the DV are made within participants rather than between groups. |
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