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PSYCH 312 1st Edition Lecture 7 Outline of Last Lecture I. MeasurementII. Scales of measurementIII. OrdinalIV. Nominal V. IntervalVI. ratioOutline of Current Lecture I. frequency distributionsa. table b. graphII. measures of central tendency a. mean b. median c. moded. shape of data seti. normal ii. skewed1. negativelyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. positivelyIII. graphing dataa. bar graphb. line graph c. examplesCurrent Lecture -Frequency distributionso1st step for getting handle on dataoIndicates how frequently the value appears in setoTable or graphExample of frequency tableShoe size Frequency5.5 16.0 26.5 2oFrequency table can be translated to frequency polygonScores on x axisFrequency of each score on y axis-Measures of central tendency oAdditional info about data provided by descriptive statsMean Mean (X): arithmetic averageTo calculate mean**Things to remember: Sensitive to all scores in setChange in 1 score-->change in meanWill be affected by extreme scoresThe sum of all scores deviations from the mean will equal zeroMedianMedian (Md): middle scoreScore that cuts the distribution into two equal halvesTo find median:Put scores in order of magnitudeIf odd # scores…Take middle scoreIf even # scores..Add two scores on either side of midpoint Divide the sum by 2**things to remember:Not sensitive to each individual scoreNot affected by extreme scores in distributionModeMode (Mo): the most frequent scoreExample scores:Distribution:1, 2, 2, 3, 5, 4, 5, 2, 4, 2Mode= 2NOTE: can be more than one mode in distributionBimodal distibutionNOTE: not all measures of CT are appropriate for all types of dataNominal data Only mode can be usedNot meaningful to talk about median & mean when talking about categorical dataOrdinal dataOnly median & mode can be usedMean is not meaningful because we cant assume that there are equal difference between the values of this particular scaleoMeasures of CT tell us the shape of data setNormal If mean=median=mode-SkewedoPositively Mean>median>modeExtreme scores on right of continuum pull the mean to rightoNegativelyMean<median<modeExtreme scores on left of continuum pull mean to leftoNOTE: better to use median vs. mean for descriptive when a set of scores is heavily skewedMean pulled in direction of skewMedian not affected by extreme scores-Graphing dataoWays to display data graphically asBar graphIV nominalLine graphIV on continuumoEither caseIV on x axisDV on Y axisoEXAMPLE 1: music experiment Plotting mean accuracy of performance in rock, classical & no musical conditionHypothetical resultsRock=25% Classical=50%No music=60%Bar graphUsed b/c IV is NOMINALoEXAMPLE 2: Memory accuracy recall under different doses of same drug (0, 50, 100 mg)Results: (mean accuracy)0 mg dose=25%50 mg dose= 50%100 mg dose= 60%Line graph Used b/c IV lies on a

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