Six Sigma and Beyond: Statistics and Probability, Volume III
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The number of observed data values below or equal to a stated value of X k .
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The stated value of X k is often called the threshold: T(X k ).
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The probability of data values less than or equal to this threshold is the sum or "cumulation" of probabilities:
where n T is the cell number n c set by the threshold T(X nT ).
Cell (X k ) | Frequency | Threshold | Cumulation, F(X k ) |
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X 1 = 2 | f 1 = 0.40 | T(X 1 ) | 0.40 |
X 2 = 3 | f 2 = 0.25 | T(X 2 ) | 0.40 + 0.25 = 0.65 |
X 3 = 4 | f 3 = 0.20 | T(X 3 ) | 0.40 + 0.25 + 0.20 = 0.85 |
X 4 = 5 | f 4 = 0.10 | T(X 4 ) | 0.40 + 0.25 + 0.20 + 0.10 = 0.95 |
X 5 = 6 | f 5 = 0.05 | T(X 5 ) | 0.40 + 0.25 + 0.20 + 0.10 + 0.05 = 1.0 |