1. Precipitation Statistics! What are the chances?

2. Weather service collects precipitation data around the country

3. Burlington Data (values in inches) How can you describe? TAKE MEAN= AVERAGE(##:##) 29.51.8 TAKE MEDIAN= MEDIAN(##:##) 26.31.9 STANDARD DEVIATION = STDEV(##:##) 4.10.9 % STANDARD DEVIATION = STDEV/MEAN*100 14% 47% MAXIMUM = MAX(##:##) 2.7 34.1 MINIMUM= MIN(##:##) 0.925.8

4. Probability... The past behavior of a system can help predict future behavior Assumes random behavior of climate system Consider chance that in any year precip amount will be exceed or be less than a stated value….”exceedence probability”

5. How to... Rank the data (n data points) Give the greatest precip year, a rank of n Give the lowest precip year, a rank of 1 Calculate the probability (p) that precip will be less than each ranked value...

6. Try an example Annual Precip for “Dullsville, KA” 199810.6” 199913.5” 200018.2” 200110.1” Rank “less than” Prob 2001 11/(4+1)or 20%10.1” 1998 22/(4+1)or 40%10.6” 1999 33/(4+1)or 60%13.5” 2000 44/(4+1)or 80%18.2”

7. Plotting on probability paper Extreme values +1  84% 50th percentile, median and mean if distribution is “normal” -1  1 Standard Deviation Include 68% of data