lecture3 - Psych 100A Winter 2010 Lecture 3: Descriptive...

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Psych 100A Winter 2010 Lecture 3: Descriptive Statistics: Numerical summaries of data: 1.Measures of location (cont.) 2.Measures of variation 1
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Calculating median Don’t use the Kiess section called “calculating the mean with the percentile formula”. Use the following procedure instead. (1) Put all the entries in order from largest to smallest. If one value is observed N times then it should appear N times in the list. (For example if three eople have score 70 then there are people have score 70 then there are three 70s in the list). There should be the same number of items in the list as mu m f m there are entries in the original data set. 2
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Calculating median (cont.) (2) If the data set contains an odd number of entries, then the median is the middle value of the ordered list. For example if we have the list 3, 3, 2, 2, 1, 1 The median is the 4th value median 1, 1. The median is the 4th value, median = 2. (3) If the data set contains an even number of entries, the median is halfway etween the two values closest to the between the two values closest to the middle of the ordered list. For example if we have the list 3, 2, 2, 1, 1, 1, then w ,,,,,, the median is (2+1)/2 = 1.5. 3
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Comparison of “central tendencies” n Media Mean Mode Qualitative + quantitative Yes No No Only one per data set Not influenced by extremes No Yes Yes No Yes Yes For grouped data, combine No Yes No 4
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Symbols for means & medians List: 1, 2, 2, 3 Mean  1223 Median Mean 4 2   2 3 , 2 , 2 , 1 midpoint Med ymbolically given n observations
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This note was uploaded on 03/15/2010 for the course PSYCHOLOGY 100B taught by Professor Firstenberg,i. during the Winter '10 term at UCLA.

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lecture3 - Psych 100A Winter 2010 Lecture 3: Descriptive...

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