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Test Review - Coggle Diagram
Test Review
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Variability
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IQR = Q3 - Q1; range of central 50% of data, resistant to outliers
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1.5xIQR Rule
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For example, min = 0, Q1 = 10, median = 15, Q3 = 16, max = 25. Are there any outliers?
IQR = 16 - 10 = 6, 1.5xIQR = 9
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Any values less than 1? Yes, the minimum is 0; 0<1, so the minimum is an outlier.
Any values greater than 25? No, the max is 25, so nothing is greater than 25.
Yes, at least we have one outlier on the low end.
Z-scores
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For example, suppose mean = 23 and SD = 10. How many SD's below the mean is a value of 12.3?
z = (obs - mean)/SD = (12.3 - 23) / 10 = -1.07; 12.3 is 1.07 SD's less than the mean because z-score negative.
Finding SD in StatCrunch: STAT -> Summary stats -> By column -> select variable of interest -> Compute
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