1. Average particle concentration at the sampling point
C1 + C2 + ... + Cn
A = ————————————
N
Where: A is the average particle concentration at a specific sampling point (grains/m³). C1 represents the particle concentration at a certain sampling point (grains/m³), and N is the number of sampling times at that point.
2. Average Mean:
A1 + A2 + ... + AL
M = —————————————
L
Where: M is the average particle concentration in the clean zone, which is the mean of the means (grains/m³). L is the total number of sampling points in the clean room (units).
3. Standard Error:
SE is the standard error of the mean of the mean (grains/m³).
4. Upper Confidence Limit (UCL):
UCL = M + t × SE
Where: UCL is the 95% confidence limit for the mean of the mean (grains/m³). The value of t is based on the t-distribution coefficient for a 95% confidence level, as shown in the table below.
T-Distribution Coefficient for 95% Confidence Limit
Sampling Point L | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | ≥9
T | 6.31 | 2.92 | 2.35 | 2.13 | 2.02 | 1.94 | 1.90 | 1.86 | —
Note: When there are more than 9 sampling points, it's not necessary to calculate the UCL.
This method provides a structured approach to analyzing air quality data in controlled environments, ensuring accurate and reliable results for maintaining cleanroom standards.
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