Determination of power and sample size for proving equivalence based on the ratio of two means for normally distributed data

The use of statistically derived alarm values for the minimisation of the risk of Cryptosporidium entering the water supply has been recommended in the report of the Bouchier expert group. Values derived using the mean plus standard deviations can be skewed by spikes, including those caused by filter washes. Indeed, theoretically, the use of standard deviations should only be used with normally distributed data. It is shown in this paper that turbidity and particle counting data is not normally distributed and that values derived by means of percentile analysis are more sensitive than using the mean plus standard deviations. Percentile analysis is able to produce alarms for data that is clearly different from normal operation, enabling smaller deviations from the usual to be identified. The values derived from one set of data are also shown to be appropriate for periods of around three months.

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Sample size determination for proving equivalence based on the ratio of two means for normally distributed data

Statistics in Medicine ◽

10.1002/(sici)1097-0258(19990115)18:1<93::aid-sim992>3.0.co;2-8 ◽

1999 ◽

Vol 18 (1) ◽

pp. 93-105 ◽

Cited By ~ 53

Author(s):

Dieter Hauschke ◽

Meinhard Kieser ◽

Edgar Diletti ◽

Martin Burke

Keyword(s):

Sample Size ◽

Sample Size Determination ◽

Distributed Data ◽

Size Determination ◽

Normally Distributed

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179. Sample Size Based Indication of Normality in Log-Normally Distributed Samples

10.3320/1.2765301 ◽

1999 ◽

Cited By ~ 1

Author(s):

N.A. Esmen ◽

G.A. Day ◽

T.A. Hall

Keyword(s):

Sample Size ◽

Normally Distributed

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Cryoscopy of Milk: Effect of Variations in the Method

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/49.3.511 ◽

1966 ◽

Vol 49 (3) ◽

pp. 511-515 ◽

Cited By ~ 1

Author(s):

R W Henningson

Keyword(s):

Statistical Analysis ◽

Sample Size ◽

Freezing Point ◽

Collaborative Study ◽

Sample Temperature ◽

Milk Samples ◽

Two Samples ◽

Temperature Rate

Abstract Bath level, sample temperature, rate of stirring, degree of supercooling, sample size, sample isolation, and refreezing of the sample were the variables in the thermistor cryoscopic method for the determination of the freezing point value of milk chosen for study. Freezing point values were determined for two samples of milk and two secondary salt standards utilizing eight combinations of the seven variables in two test patterns. The freezing point value of the salt standards ranged from –0.413 to –0.433°C and from –0.431 to –0.642°C. The freezing point values of the milk samples ranged from –0.502 to –0.544°C and from –0.518 to –0.550°C. Statistical analysis of the data showed that sample isolation was a poor procedure and that other variables produced changes in the freezing point value ranging from 0.001 to 0.011°C. It is recommended that specific directions be instituted for the thermistor cryoscopic method, 15.040–15.041, and that the method be subjected to a collaborative study.

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Determination of the Sensitivity of a RapidEscherichia coli O157:H7 Assay for Testing 375-Gram Composite Samples

Applied and Environmental Microbiology ◽

10.1128/aem.66.9.4149-4151.2000 ◽

2000 ◽

Vol 66 (9) ◽

pp. 4149-4151 ◽

Cited By ~ 16

Author(s):

Wan-Ling Tsai ◽

Cynthia E. Miller ◽

Edward R. Richter

Keyword(s):

Escherichia Coli ◽

Sample Size ◽

Ground Beef ◽

Immunomagnetic Separation ◽

Enzyme Linked Immunosorbent Assay ◽

Elisa System ◽

Composite Ground ◽

Single Size ◽

Composite Samples

ABSTRACT Both 25-g single-size ground beef samples and 375-g composite ground beef samples were tested by a method combining an immunomagnetic separation (IMS) technique with a sandwich enzyme-linked immunosorbent assay (ELISA) system (IMS-ELISA). The results demonstrated that IMS-ELISA could detect the target, Escherichia coliO157:H7, at the level of 10−1 CFU/g of sample in either the 25- or 375-g sample size.

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