PSYC 331 Lecture 9-- FD and Graphs

# PSYC 331 Lecture 9-- FD and Graphs - PSYC 331 Lecture 9...

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1 PSYC 331 Lecture 9 Frequency Distributions and Graphs

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2 Overview In this lecture we will: Discuss descriptive statistics Work with ungrouped and grouped frequency distributions Work with percentiles and percentile rank Learn about 4 ways of graphically representing data
3 Descriptive Statistics -- Review Used to describe, summarize, and tabulate the data This includes: 1. Determining how many participants got each score 2. Providing information on the standing of a given score in relation to the rest of the sample 3. Graphically summarizing the set of scores (to allow inspection of the dispersion or variability of the scores) 4. Numerically summarizing the variability of the scores 5. Determining the central tendency of the set of scores (the location of the 'middle' score)

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4 Frequency Distribution Is a record of the number of individuals/ participants located in each category on the scale of measurement Allows the researcher a way of seeing the entire distribution at a "glance". Provides the following information: 1. The standing of a particular score relative to all other scores, 2. How many participants got each score, 3. Central tendency (the "average" or "middle" scores), and 4. The variability of a set of scores (how "spread out" the scores are).
5 Frequency Distribution Example Assume we have scores from a 100 point exam given in Introductory Psychology. Fifty students took the exam. We want to see the ungrouped frequency distribution of the scores. To do this: 1. List all possible scores in the distribution in a column from highest to lowest. 2. Count the number of times the score occurs in the distribution and list this value in the frequency column. 3. Check your results to make sure you counted every observation. Note that Σ freq. = n (total number of participants).

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6 Ungrouped Frequency Distribution Step 1 (List): Step 2 (Count): Step 3 (Check):
7 Grouped Frequency Distribution Presents the results as ‘groups’ of

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## This note was uploaded on 01/15/2010 for the course PSYC 331 taught by Professor Dianealonso during the Fall '09 term at UMBC.

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PSYC 331 Lecture 9-- FD and Graphs - PSYC 331 Lecture 9...

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