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# PSY 206 Final

### Finals

Question | Answer |
---|---|

Magnitude | (1) a property of measurement in which the ordering of numbers reflects the ordering of the variable (2) An indication of the strength of the relationship between two variables |

Scatterplot | A figure that graphically represents the relationship between 2 variable |

Causality | The assumption that a correlation indicates a causal relationship between 2 variables |

Directionality | The inference made with respect to the direction of a causal relationship between 2 variables |

Third-variable problem | The problem of a correlation between two variables being dependent on another (third) variable Ex. ice cream consumption and drowning |

Partial correlation | A correlation technique that involves measuring three variables and then statistically removing the effect of the third variable from the correlation of the remaining 2 |

Restrictive Range | A variable that is truncated and has limited variability Ex. SAT scores and GPA |

Person-who argument | Arguing that a well-established statistical trend is invalid because we know a "person who" went against the trend |

Between-participants design | An experiment in which different participants are assigned to each group |

Posttest-only control group design | An experimental design in which the dependent variable is measured after the manipulation of the independent variable |

Pretest/posttest control group | An experimental design in which the dependent variable is measured both before and after manipulation of the independent variable |

History effect | Changes in the dependent variable may be due to outside events that take place during the course of the study Minimize: Use an equivalent control group |

Nonequivalent control group | Problems in participant selection or assignment may lead to important differences between the participants assigned to the experimental and control groups Minimize: Random sampling and random assignment |

Maturation effect | Changes in the dependent variable may be due to participants maturing (growing older) during the course of the study Minimize: Use an equivalent control group |

Testing effect | Changes in the dependent variable may be due to participants being tested repeatedly and getting either better or worse because of the repeated testing Minimize: use and equivalent control group |

Regression to the mean | Participants who are selected for a study because they are extreme (high or low) on some variable may regress toward that mean and be less extreme at a later testing Minimize: equivalent group of participants with extreme scores |

Instrumentation effect | Changes in the dependent variable may be due to changes in the measuring device, either human or machine Minimize: equivalent control group |

Mortality | Differential attrition or dropout in the experimental and control groups may lead to inequality between the groups Minimize: monitor for differential loss of participants in experimental and control groups |

Diffusion of treatment | Changes in the behaviors or responses of participants may be due to information they have received from others participating in the study Minimize: testing participants all at once |

Experimenter and subject effects | Either experimenters or participants consciously of unconsciously affect the results of the Minimize: Double-blind study |

Floor and ceiling effects | the measuring instrument used is not sensitive enough to detect differences Minimize: ensure the measuring device is reliable and valid before the study |

Single-blind experiment | An experimental procedure in which either the participants or the experimenter are blind to the manipulation being made |

Double-blind experiment | An experimental procedure in which neither the experimenter nor the participant knows the condition to which each participant has been assigned; both parties are blind to the manipulation |

Placebo group | a group or condition in which participants believe they are receiving treatment but are not |

Placebo | an inert substance that participants believe is a treatment |

External validity | the extent to which the results of an experiment can be generalized |

college sophomore problem | results from using mainly college sophomores as participants in research studies |

exact replication | repeating a study using the same means of manipulating and measuring the variables as in the original study |

conceptual replication | a study based on another study that uses different methods, a different manipulation, or a different measure |

systematic replication | a study that varies from an original study in one systematic way Ex: using a different number or type of participants |

factorial design | a design with more that one independent variable (herbal supplement (two types) and rehearsal (two types) |

factorial notation | the notation that indicates how many independent variables are used in a study and how many levels are used for each Ex. 2x2 (2 independent variables with 2 levels each) |

main effect | an effect of a single independent variable Ex: in a study with 2 independent variables, 2 main effects are possible |

interaction effect | the effect of each independent variable across the levels of the other independent variable Ex: herbal supplement and rehearsal type |

correlated-groups design | an experimental design in which the participants in the experimental and control groups are related in some way Ex: within and between participant designs |

within-participants design | a type of correlated- groups design in which the same participants are used in each condition Ex: TV violence (both groups view violent and nonviolent programs) |

order effects | the order of the conditions has an effect on the dependent variable Ex: viewing a violent tv program could influence the nonviolent tv program |

counterbalancing | a mechanism for controlling order effects either by including all orders of treatment presentation or by randomly determining the order for each participant Ex: half watch the violent then the nonviolent while half watch nonviolent then violent |

cross-sectional design | a type of developmental design in which participants of different ages are studied at the same time Ex:a researcher interested in cog abilities across ages might study groups of 5-year-olds, 8-year-olds, and so on |

cohort | a group of individuals born at about the same time Ex:Me and other 19-year-olds |

cohort effect | a generational effect in a study that occurs when the eras in which individuals are born affect how they respond in the study Ex:the cog abilities of the 5-year-olds may be different from the 11-year-olds because of how/when they were raised |

longitudinal design | a type of developmental design in which the same participants are studied repeatedly over time as they age Ex:study the cog abilities of 5-year-olds every 3 years |

sequential design | a developmental design that is a combination of the cross-sectional and longitudinal designs Ex:study the cog abilities of each of the groups every 3 years |

frequency distributions | A list of all scores occurring in the distribution along with the frequency of each Use with: nominal, ordinal, interval, or ratio data Ex |

class interval frequency distribution | a table in which the scores are grouped into intervals and listed along with the frequency of scores in each interval |

qualitative variable | a categorical variable for which each value represents a discrete category Ex: gender |

bar graph | A pictorial graph with bars representing the frequency of occurrence of items for qualitative variables Use with: Nominal data |

quantitative variable | a variable for which the scores represent a change in quantity Ex: temperature |

histogram | A pictorial graph with bars representing the frequency of occurrence of items for quantitative variables Use with: ordinal, interval, or ratio data |

frequency polygon | a line graph of the frequencies of individual scores Ex: IQ score data |

descriptive statistics | numerical measures that describe a distribution by providing information on the central tendency of the distribution, the width of the distribution, and the shape of the distribution Ex: mean, median, mode, skew, kurtosis |

measure of central tendency | a number that characterizes the "middleness" of an entire distribution Ex:mean, median, and mode |

mean | the arithmetic average Use with: interval and ratio |

median | the middle score in a distribution of scores organized from highest to lowest or lowest to highest Use with: ordinal, interval, and ratio |

mode | the score occurring with the greatest frequency Use with: nominal, ordinal, interval, or ratio data |

measure of variation | a number that indicates the degree to which scores are either clustered or spread in a distribution Ex: range, standard deviation |

range | a measure of variation; the difference between the lowest and highest scores in a distribution Ex: 7-2=5 |

standard deviation | the square root of the average squared deviation from the mean of the distribution |

variance | the standard deviation squared |

normal curve | a symmetrical bell-shaped frequency polygon representing a normal distribution |

normal distribution | a theoretical frequency distribution that has certain special characteristics |

kurtosis | how flat or peaked a normal distribution is |

mesokurtic | normal curves that have peaks of medium height and distributions that are moderate in breadth |

leptokurtic | normal curves that are tall and thin with only a few scores in the middle of the distribution having a high frequency |

platykurtic | normal curves that are short and relatively more dispersed (broader) |

positively skewed distribution | a distribution in which the peak is to the left of the center point and the tail extends toward the positive direction |

negatively skewed distribution | a distribution in which the peak is to the right of the center point and the tail extends in the negative direction |

z-score (standard score) | a number that indicates how many standard deviation units a raw score is from the mean of a distribution |

standard normal distribution | a normal distribution with a mean of 0 and a standard deviation of 1 |

probability | the expected relative frequency of a particular outcome |

percentile rank | a score that indicated the percentage of people who scored at or below a given raw score Ex: iowa testing |

Pearson product-moment correlation coefficient (Pearson's r) | the most commonly used correlation coefficient when both variables are measured on an interval or ratio scale Ex: height and weight ratio |

coefficient of determination (r2) | a measure of the proportion of the variance in one variable that is accounted for by another variable; calculated by squaring the correlation coefficient Ex: tells us how much of the variation in weight is accounted for in the variation of height |

Spearman's rank-order correlation coefficient | the correlation coefficient used when one or more of the variables are measure on an ordinal scale |

point-biserial correlation coefficient | the correlation coefficient used when one of the variables is measured on a dichotomous nominal scale and the other is measured on an interval or ratio scale |

phi coefficient | the correlation coefficient used when both measured variables are dichotomous and nominal |

regression analysis | a procedure that allows us to predict an individual's score on one variable based on knowing one or more other variables Ex: predicting SAT score based off of GPA |

regression line | the best-fitting straight line drawn through the center of a scatterplot that indicates the relationship between the variables |

null hypothesis | states that the independent variable has no effect and that there is no difference between the 2 groups Ex: Ho:uo=u1 |

alternative hypothesis | states that the independent variable has an effect and that there is a difference between the 2 groups Ex: Ha: uo>u1 |

two-tailed test | states that a difference is expected between the groups, but there is no prediction as to which groups will perform better or worse Ex: IQ scores in kids in after school programs and those that aren't |

one-tailed test | states that a difference is expected between the groups, and it is expected to occur in a specific direction Ex: kids in after school programs are smarted than those who aren's |

type I error | saying there is a difference between the groups when there isn't Ex: saying kids in after school programs are smarter when they aren't |

type II error | saying that there is not a difference between the groups when in reality there is Ex: saying kids in after school programs aren't smarter when they are |

statistical significance | the probability of a type I error is low (<.05) |

parametric test | a statistical test that involves making assumptions about estimates of population characteristics Ex: you know the mean and standard deviation (t test) |

nonparametric test | a statistical test that does not involve the use of any population parameters Ex: you don't know the mean or standard deviation |

independent-groups t test | a parametric inferential test for comparing sample means of two independent groups of score |

standard error of the difference between means | the standard deviation of the sampling distribution of differences between the means of independent samples in a two-sample experiment |

degrees of freedom (df) | the number of scores in a sample that are free to vary (based off of the participants) Ex: 76 (control)+ 26 (experimental)-2= 120 |

effect size | the proportion of variance in a dependent variable that is accounted for by the manipulation of the independent variable Ex: cohen's d- the larger the effect size the better |

Cohen's d | an inferential statistic for measuring effect size Ex:small effect size is .20, medium is .50 and large is .80 |

Bonferroni adjustment | setting a more stringent alpha level for multiple tests to minimize type I errors Ex: going form .05 to .01 |

ANOVA (analysis of variance) | an inferential statistic test for comparing the means of three or more groups Ex: exercise for small amount, medium amount, and a lot and then measure stress |

one-way randomized ANOVA | compares the means for 3 or more groups using a between-participants design and one independent variable Ex: type of rehearsal- rote, story,and imagery |

grand mean | the mean performance across all participants in a study Ex: all of the results added together and divided by 3 |

error variance | the amount of variability among the scores caused by chance or uncontrolled variables |

within-groups variance | the variance within each condition, an estimate of the population error variance |

between-groups variance | an estimate of the effect of the independent variable and the error variance |

F-ratio | the ratio of between-groups variance to within- groups variance |

total sum of squares | the sum of the squared deviations of each score from the grand mean |

within-groups sum of squares | the sum of the squared deviations of each score from its group mean |

between-groups sum of squares | the sum of the squared deviations of each group's mean from the grand mean, multiplied by the number of participants in each group |

mean square | an estimate of either variance between groups or variance within groups |

eta-squared | a measure of effect size; the variability in the dependent variable that is attributable to the independent variable |

post hoc test | a means of comparing all possible pairs of groups to determine which ones differ significantly from each other |

Tukey's post hoc test | a test conducted in order to determine which conditions in a study with more than 2 groups differ significantly from each other |