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Unformatted text preview: Next Previous Section 4.2: Elementary Statistics Section 4.2: Elementary Statistics 11 Elementary Statistics Sample Distributions Mean Median Standard Deviation Sample size effects Section 4.2: Elementary Statistics Next Previous Section 4.2: Elementary Statistics Section 4.2: Elementary Statistics 22 Usually, only a sample of a population is measured The results are then taken to represent the entire population Example: Determine the amount of lumber in a wooded area Method: Measure a few trees in a sample area to obtain an approximate average diameter and height Count the number of trees in sample area Use results to estimate the total wood in the sample area Extrapolate results to entire forest The usefulness of statistics Next Previous Section 4.2: Elementary Statistics Section 4.2: Elementary Statistics 33 Magnitude: Size of a variable Observation: Result of a single measurement Parent Population: Collection of all possible measurements Sample: A finite group of measurements Error: Deviation from the true value Accuracy: Closeness to the true value Precision: Closeness of a grouping to each other Precision k Accuracy Maybe you can measure precisely to 0.1 mm But you could be quite wrong if ruler is 25 mm too short Some useful statistical terms Next Previous Section 4.2: Elementary Statistics Section 4.2: Elementary Statistics 44 Histogram: Frequency of occurrence vs. Value Example: Grades on a quiz grade # of grades value 4 2 5 4 6 7 7 8 8 6 9 3 10 2 32 total grades Frequency Value The distribution of values grade values # of grades Next...
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This note was uploaded on 05/19/2008 for the course ENGR 25 taught by Professor All during the Spring '08 term at Lehigh University .
 Spring '08
 ALL

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