The Average Varroa chart shows the national monthly average varroa level based on all samples and all years in the APHIS survey, charted as a line. The error bars are based on the 95% confidence interval which represents the range that 95% of all samples are within. The error bars for the sentinel site averages represent the minimum and maximum varroa levels found. Months without columns have no samples taken during those months.
The Average Nosema chart shows the national monthly average nosema level, compared to the selected sentinel sites using the same methodology as the Average Varroa chart.