AAVSO: American Association of Variable Star Observers
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Day-to-Day Variation in Estimates of Sunspot Group Totals (Abstract)

Volume 31 number 1 (2003)

Carl E. Feehrer

Abstract

(Abstract only) Observers who are learning the art of sunspot counting and who recognize the importance of correctly estimating the numbers of groups present sometimes ask how much variation in the group total can be expected from day to day. For example, if one had decided that five groups were present on one day, could an estimate of seven groups on the following day be considered reasonable? Three groups? Five groups again? With the objective of being able to provide observers with appropriate expectations, this paper presents the results of a brief statistical study of AAVSO Solar Committee estimates that was aimed at discovering the probabilities of changes of various amounts in the mean estimates of group numbers over successive days. The results suggest that the probability of estimating the same numbers on successive days is equal to 0.255; of plus or minus one, 0.484; of plus or minus two, 0.160; of plus or minus three, 0.089; of plus or minus four, 0.012. No differences beyond four were found.