Chapt 5 - DESCRIBING AND PRESENTING DATA Criteria of a Good...

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DESCRIBING AND PRESENTING DATA Criteria of a Good Description Looking at all of the raw data is too overwhelming, hard to get an overview of what is going on need to summarize and describe the data Three criteria that make data description/summary the most useful Accurate Concise Understandable Frequency distribution Starting point for many data descriptions is the frequency distribution Table/Graph that summarizes raw data by showing the number of scores that fall within each of several categories Simple Grouped easier to grasp info in frequency distributions when graphed histograms (interval or ratio—equal distances are meaningful) bar charts (nominal and ordinal)—separated bars Horizontal—x-axis—always presents scores/class intervals
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Vertical—y-axis—always presents frequencies—number of scores in each class interval Helping behavior observed in 2 different Groups experimental (awareness) vs control condition #s indicate the degree to which an Observer rated each participant as helpful 1 = not at all to 5 = extremely helpful C D 1.00 1.00 1.00 2.00 1.00 2.00 2.00 2.00 2.00 3.00 3.00 3.00 3.00 3.00 4.00 3.00 4.00 3.00 4.00 4.00 5.00 4.00 5.00 5.00 First step—-always check out frequencies Frequency Table C D | |Frequency|Percent| |Frequency|Percent| |-----|||||-------|-------|| |---------|-------| | 1.00 |||||3 |25.0 || |1 |8.3 | | ----- |||||-------|-------|| |---------|-------| | 2.00 |||||2 |16.7 || |3 |25.0 | | ----- |||||-------|-------|| |---------|-------| | 3.00 |||||2 |16.7 || |5 |41.7 | | ----- |||||-------|-------|| |---------|-------| | 4.00 |||||3 |25.0 || |2 |16.7 | | ----- |||||-------|-------|| |---------|-------|
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| 5.00 |||||2 |16.7 || |1 |8.3 | |-----|||||-------|-------|| |---------|-------| |Total|||||12 |100.0 || |12 |100.0 | Bar Charts Experimental Condition =>awareness of differences in helping behavior manipulation C C 5.00 4.00 3.00 2.00 1.00 Frequency 3.5 3.0 2.5 2.0 1.5 1.0 .5 0.0 Control Condition =>no manipulation
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D D 5.00 4.00 3.00 2.00 1.00 Frequency 6 5 4 3 2 1 0 Measures of Central Tendency frequencies convey important info about participants’ responses also want numbers that summarize an entire group of participants Measures of central tendency convey info about distribution by providing info about the average or most typical scores Three measures of CT most typically used—all tell us something slightly different about the data Mean—average Sum scores for all cases and then divide by number of cases does not always accurately represent the average or typical case, look at the median and mode
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Median Middle score of distribution—rank order scores, median is the one ranked in the middle Odd number, clear; even, pick number in middle Advantage over mean—less affected by extreme scores— outliers Mode Most frequent score Sometimes no mode or can be multiple modes
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This note was uploaded on 04/22/2008 for the course PSYCH 31:043 taught by Professor Klohnen during the Spring '08 term at University of Iowa.

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Chapt 5 - DESCRIBING AND PRESENTING DATA Criteria of a Good...

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