Week2_Notes

# Week2_Notes - Psych 100A Week 2 Useful Formulas and...

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Psych 100A Week 2 Useful Formulas and Procedures Dawn Chen October 9, 2009 Notation Population parameter Sample statistic Mean μ x Standard deviation σ s Variance 2 2 s Size of pop./sample N n Measures of Central Tendency Mean 1 N i i x N = = 1 n i i x x n = = Median ( 29 ( 29 th th 2 2 th obs 1 obs if is even 2 1 obs if is odd 2 n n n n n + + + Mode Most frequent observation Measures of Variability Range max obs – min obs 75 th percentile (Q3) – 25 th percentile (Q1) IQR ( 29 th th th th obs 1 obs if is an integer Let , percentile 2 100 obs if is not an integer m m m np m p m m + + = = Variance 2 2 1 ( ) N i i x N = - = 2 2 2 2 1 1 ( ) 1 1 n n i i i i x nx x x s n n = = - - = = - - Standard deviation 2 = + 2 s s = +

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How to Construct a Boxplot (1) Draw the x -axis for the boxplot based on the range of values. (2) Calculate the mean, median, Q1, Q3, and IQR. (3) Draw a box above the x -axis whose left side corresponds to Q1 and whose right side corresponds to Q3. (4) Draw a line inside the box corresponding to the median. (5) If requested, draw a point inside the box corresponding to the mean. (6) Indicate outliers that are less than Q1 – 3 × IQR or greater than Q3 + 3 × IQR with closed dots. (7) Indicate outliers that are less than Q1 – 1.5 × IQR or greater than Q3 + 1.5 × IQR but that were not marked in (6) with open dots. (8)
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## This note was uploaded on 09/24/2010 for the course STATS 13a taught by Professor Chen during the Spring '10 term at UCLA.

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Week2_Notes - Psych 100A Week 2 Useful Formulas and...

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