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Unformatted text preview: 1 THINKING CRITICALLY: THINKING CRITICALLY: Part 2 Part 2 100 100 Sep 22 Sep 22 08 08 Overview Overview Define statistics & difference between descriptive & inferential Common measuring scales and what we can do with them Shapes of distributions Measures of central tendency (of the centre of a distribution) Measures of dispersion (of the spread of a distribution) Correlations (strength, direction) Lying with statistics Learning Objectives Learning Objectives Define statistics & difference between descriptive & inferential Understand the following measuring scales: nominal, ordinal, interval & ratio Understand what kinds of statistics are permissible with data from each scale Explain how graphs can be used to misrepresent data Describe and use three measures of central tendency, and tell which is most affected by extreme scores Describe and use two measures of variability: range & standard deviation Identify factors that affect generalizability of findings Explain how psychologists decide whether differences are meaningful; understand the difference between statistical significance and practical significance Explain the value of simplified laboratory conditions in discovering general principles of behavior 2 Statistics is/are Statistics is/are The mathematics of the collection, organization, and interpretation of numerical data, especially the analysis of population characteristics by inference from sampling A branch of mathematics dealing with the collection, analysis, interpretation, and presentation of masses of numerical data A set of data (i.e. vital statistics) Three kind of lies: Lies, damned lies, and statistics. Types of Statistics Types of Statistics Inferential Statistics: A set of procedures for making decisions about hypotheses. A set of procedures for reaching conclusions that extend beyond the data. These procedures help us make inferences from the sample about the population from which it was drawn. Descriptive Statistics: Descriptive statistics are simple descriptions of what the data show; they are quantitative or pictorial summaries of the data. Descriptive statistics refers to a set of procedures /methods used for describing the basic features of the data in a study. Measurement Scales Measurement Scales Measurement is the assignment of numbers or other labels to objects or events in a systematic fashion Four levels of measurement (or scales) are commonly used: Nominal, Ordinal, Interval, Ratio We will briefly consider: the measurement principle involved for each scale...
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- Fall '09