AF Sections 2.5-2.6 handouts

AF Sections 2.5-2.6 handouts - STAT 2000 Measures of...

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1 STAT 2000 Sections 2.5-2.6 Measures of Position Statistics: The Art and Science of Learning from Data Agresti-Franklin Measures of Position Percentiles The pth percentile is the value below which you have p% of the data. Example : If a value lies at the 30 th percentile, then approximately 30% of the values are less than this value, and approximately 70% of the values are greater than this value. Notation : P 30 is the 30 th percentile. If John graduated at the 78th percentile in a class of 876, approximately how many students ranked below John? Joan learned that she would graduate ranked 47th (from the top) in a class of 876. Joan graduated at the _____ percentile of her class. Measures of Position: Quartiles Quartiles divide the data into 4 equal parts. 25% | 25% | 25% | 25% Q1 Q2 Q3 Q1: First Quartile is the 25 th percentile. (25% below and 75% above) Q2: Second Quartile is the 50 th percentile. (50% below and 50% above) Q2 is also the median. Q3: Third Quartile is the 75 th percentile. (75% below and 25% above) 25% | 25% | 25% | 25% Q1 Q2 Q3 P 25 P 50 P 75 median Finding Quartiles First find the median. Then find the middle value of the upper and lower halves. Remember the data must be in order! Data: 20 19 30 18 17 22 Data 20 19 30 18 17 22 23
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2 66 70 69 80 68 67 72 73 70 57 63 70 Use technology to find the quartiles for the temperature at launch data for space shuttle missions up to and including Challenger. (Challenger was 31 degrees.) 78 67 53 67 75 70 81 76 79 75 76 58 31 Descriptive Statistics: Temperature Total Variable Count Mean StDev Minimum Q1 Median Q3 Maximum Temperature 25 68.44 10.53 31.00 67 70.00 75 81.00 Calculated using StatCrunch Measuring Spread using Quartiles Interquartile Range – IQR IQR = Q3 – Q1 The IQR is the range of the middle 50% of the data.
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This note was uploaded on 03/22/2009 for the course STAT 2000 taught by Professor Smith during the Spring '08 term at UGA.

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AF Sections 2.5-2.6 handouts - STAT 2000 Measures of...

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