1. Lecture 2 Forestry 3218 Lecture 2 Statistical Methods Avery and Burkhart, Chapter 2 Forest Mensuration II Avery and Burkhart, Chapter 2

2. Lecture 2 Forestry 3218 Bias, Accuracy, Precision Bias – systematic distortion of measurements – sources: measurement flaw, incorrect sampling method Accuracy – success of estimating the true value of a quantity Precision – clustering of sample values about their own average

3. Lecture 2 Forestry 3218 Bias, Accuracy, Precision PreciseImprecise UnbiasedBiased

4. Lecture 2 Forestry 3218 Independent events Mutually exclusive Calculating Probabilities Relative frequency with which an event takes place in the long run

5. Lecture 2 Forestry 3218 Population vs. Sample Population – The aggregate of all arbitrarily defined, nonoverlapping sample units – Finite vs. infinite Sample – An aggregation of sample units from which measurements or observations are taken

6. Lecture 2 Forestry 3218 Parameter vs.Variable Parameter – A constant that describes the population as a whole Variable – A characteristic that may vary from one sample to the next

7. Lecture 2 Forestry 3218 Frequency Distribution The relative frequency of different values that occur of a variable in a population Types – Normal – Binomial – Poisson

8. Lecture 2 Forestry 3218 Statistical computations Mean (the average) Median (the middle value) Mode (the most frequently appearing value)

9. Lecture 2 Forestry 3218 Statistical computations (measures of dispersion) Range – Easy to compute – Fails to take into account how the data are distributed Variance – A measure of dispersion among individual observations about their average value Standard deviation (s)

10. Lecture 2 Forestry 3218 Coefficient of variation – A percentage of the standard deviation to the mean of a sample – Allows a comparison of relative variability about different-sized means Statistical computations (measures of dispersion)

11. Lecture 2 Forestry 3218 Standard error of the mean – A measure of variation of among sample means – A standard deviation among the means of samples of a fixed n Statistical computations (measures of dispersion) – when sampling from a finite population Calculation – for simple random sampling from an infinite population

12. Lecture 2 Forestry 3218 Confidence limit The confidence limits for population mean Mean  t(standard error)

13. Lecture 2 Forestry 3218 Review