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AP Psychology Page 1 of 5 Tutorial: Basic Statistics Study Guide ____________ ' Copyright 2002 Apex Learning, Inc. All rights reserved. This material is intended for the exclusive use of registered users only. No portion of these materials may be reproduced or redistributed in any form without the express written permission of Apex Learning, Inc. Key Terms from the Presentation You should be able to explain each of these in your own words, and be able to recognize situations where each one applies: descriptive statistics inferential statistics histograms statistical significance mode mean median standard deviation How do Descriptive Statistics Help Researchers Understand Data? After the initial collection of data, the researcher must organize it. A first step is to list all the possible responses and how often each one occurred. This is a frequency graph , or frequency distribution . A frequency distribution is usually depicted in a graph such as a histogram , or a polygon. Here, for instance, is a histogram of weights on a football team. Each bar represents the number of people who fall within a certain weight range. 150- 160- 170- 180- 190- 200- 210- 220- 230- 240- 160 170 180 190 200 210 220 230 240 250 14 12 10 8 6 4 2 0 F R E Q U E N C Y WEIGHT Measure of Central Tendency and Variability A measure of central tendency is a single number that people use to represent an entire data set. Usually it’s considered to be the "middle" of the data set. There are three measures of central tendency that are used to express the central point of a distribution of numbers: the mode : the most commonly occurring response(s) the median : the halfway point between the lowest and highest number the mean : the "average," or all of the numbers added up and divided by the total number of observations. The mean is the measure that most people think of when they hear the word "average." Researchers also need a measure of variability , or how much variety there is in the data. This is especially useful to researchers when they want to make inferences about a whole population based on a sample. There are three measures of variability:
AP Psychology Page 2 of 5 Tutorial: Basic Statistics Study Guide ____________ ' Copyright 2002 Apex Learning, Inc. All rights reserved. This material is intended for the exclusive use of registered users only. No portion of these materials may be reproduced or redistributed in any form without the express written permission of Apex Learning, Inc.

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