Hockenbury Discovering Psychology 5th txtbk

Concept MapA-15CONCEPTMAPSTATISTICS: UNDERSTANDING DATAStatisticsA branch of mathematics that researchersuse to organize and interpret dataDescriptive StatisticsSummaries of data that makethe data meaningful and easyto understandFrequency distribution:• Summary of how often variousscores occur in a sample ofscores• Can be presented in the formof a table, a histogram, or afrequency polygon• Can be symmetrical distributionor asymmetrical (skewed distribution)• Standard normal curve: A symmetricaldistribution forming abell-shaped curve in which themean, median, and mode areall equal and fall in the exactmiddleCorrelation refers to the relationshipbetween two variables.Measures of variability show howclosely scores in a distribution aregrouped.• Range: The highest score minus thelowest score• Standard deviation: The square rootof the sum of the squared deviationsaround the mean divided by the numberof scores; eliminates the problemof negative deviations• z score: Shows how far away from themean a score is in terms of standarddeviation units• Positive correlation: As onevariable increases in size, the secondvariable also increases.• Negative correlation: As one variableincreases in size, the second variabledecreases.• A correlational relationship is notnecessarily a causal relationship.• Correlation can be presented visuallyin a scatter diagram orscatter plot.Measures of centraltendency of a distribution:• Mode: Most frequentscore• Median: Middle score inthe distribution• Mean: Arithmetic averageof scores; usually the bestoverall representation ofcentral tendency, but influencedby very high orvery low scoresInferential Statistics• Used to determine whether a study’soutcomes can be generalized to alarger population• Provide information about whethera study’s findings are statisticallysignificantPopulation: A complete set ofsomethingSample: A subset of a populationt-test: Technique used to comparethe means of two groups