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Psychology Statistics Study Guide

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Psychology Statistics Study Guide

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  • June 2013
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Descriptive statistics
information Descriptive statistics organize, summarize, and communicate a group of numerical observations and describe large amounts of data in a single number or in just a few numbers Inferential statistics

Use samples to draw conclusions about a population Inferential statistical use sample data to make general estimates about the larger population, and infer or make an intelligence guess about, the population Sample: a set of observations drawn from the population of interest. Samples are used most often because it is rare that we are able to study every person (or organization or laboratory rat) in a particular population. Researchers usually study a sample, but they are really interested in the population, which includes all possible observations about which we’d like to know something. Discrete Variables that can only take on specific values (e.g., whole numbers) How many letters are in your name? * Continuous Can take on a full range of values, How tall are you? Variables are observations of physical, attitudinal, and behavioral characteristics that can take on different values. We use both discrete and continuous numerical observations to quantify variables. Discrete observations can take on only specific values (e.g., whole numbers); no other values can exist between these numbers. Continuous observations can take on a full range of values (e.g., numbers out to several decimal places); an infinite number of potential values exists. Two types of observations are always discrete: nominal and ordinal variables. Two types of observations that can be continuous are interval variables and ratio variables. Interval variables are used for observations that have numbers as their values; the distance (or interval) between pairs of consecutive numbers is assumed to be equal. For examples, time is an interval variable because the interval from one second to the next is always the same. Some interval variables are also discrete...