# Statistical Methods in Practice: for Scientists and Technologists

ISBN: 978-0-470-74664-6
246 pages
September 2009

## Description

This is a practical book on how to apply statistical methods successfully. The Authors have deliberately kept formulae to a minimum to enable the reader to concentrate on how to use the methods and to understand what the methods are for. Each method is introduced and used in a real situation from industry or research.

Each chapter features situations based on the authors’ experience and looks at statistical methods for analysing data and, where appropriate, discusses the assumptions of these methods.

Key features:

• Provides a practical hands-on manual for workplace applications.
• Introduces a broad range of statistical methods from confidence intervals to trend analysis.
• Combines realistic case studies and examples with a practical approach to statistical analysis.
• Features examples drawn from a wide range of industries including chemicals, petrochemicals, nuclear power, food and pharmaceuticals.
• Includes a supporting website, providing software to aid tutorials.

Scientists and technologists of all levels who are required to design, conduct and analyse experiments will find this book to be essential reading.

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Preface.

1 Samples and populations.

Introduction.

What a lottery!

No can do.

Nobody is listening to me.

How clean is my river?

Discussion.

2 What is the true mean?

Introduction.

Presenting data.

Averages.

Measures of variability.

Relative standard deviation .

Degrees of freedom.

Confidence interval for the population mean.

Sample sizes.

How much moisture is in the raw material?

Problems.

3 Exploratory data analysis.

Introduction.

Histograms: is the process capable of meeting specifications?

Box plots: how long before the lights go out?

The box plot in practice.

Problems.

4 Significance testing.

Introduction.

The one-sample t -test.

The significance testing procedure.

Confidence intervals as an alternative to significance testing.

Confidence interval for the population standard deviation.

F-test for ratio of standard deviations.

Problems.

5 The normal distribution.

Introduction.

Properties of the normal distribution.

Example.

Setting the process mean.

Checking for normality.

Uses of the normal distribution.

Problems.

6 Tolerance intervals.

Introduction.

Example.

Confidence intervals and tolerance intervals.

7 Outliers.

Introduction.

Grubbs’ test.

Warning.

8 Significance tests for comparing two means.

Introduction.

Example: watching paint lose its gloss.

The two-sample t -test for independent samples.

An alternative approach: a confidence intervals for the difference between population means.

Sample size to estimate the difference between two means.

A production example.

Confidence intervals for the difference between the two suppliers.

Sample size to estimate the difference between two means.

Conclusions.

Problems.

9 Significance tests for comparing paired measurements.

Introduction.

Comparing two fabrics.

The wrong way.

The paired sample t -test.

Presenting the results of significance tests.

One-sided significance tests.

Problems.

10 Regression and correlation.

Introduction.

Obtaining the best straight line.

Confidence intervals for the regression statistics.

Extrapolation of the regression line.

Correlation coefficient.

Is there a significant relationship between the variables?

How good a fit is the line to the data?

Assumptions.

Problems.

11 The binomial distribution.

Introduction.

Example.

An exact binomial test.

A quality assurance example.

What is the effect of the batch size?

Problems.

12 The Poisson distribution.

Introduction.

Fitting a Poisson distribution.

Are the defects random? The Poisson distribution.

Poisson dispersion test.

Confidence intervals for a Poisson count.

A significance test for two Poisson counts.

How many black specks are in the batch?

How many pathogens are there in the batch?

Problems.

13 The chi-squared test for contingency tables.

Introduction.

Two-sample test for percentages.

Comparing several percentages.

Where are the differences?

Assumptions.

Problems.

14 Non-parametric statistics.

Introduction.

Descriptive statistics.

A test for two independent samples: Wilcoxon–Mann–Whitney test.

A test for paired data: Wilcoxon matched-pairs sign test.

What type of data can be used?

Example: cracking shoes.

Problems.

15 Analysis of variance: Components of variability.

Introduction.

Overall variability.

Analysis of variance.

A practical example.

Terminology.

Calculations.

Significance test.

Variation less than chance?

When should the above methods not be used?

Between- and within-batch variability.

How many batches and how many prawns should be sampled?

Problems.

16 Cusum analysis for detecting process changes.

Introduction.

Analysing past data.

Intensity.

Localised standard deviation.

Significance test.

Yield.

Conclusions from the analysis.

Problem.

17 Rounding of results.

Introduction.

Choosing the rounding scale.

Reporting purposes: deciding the amount of rounding.

Reporting purposes: rounding of means and standard deviations.

Recording the original data and using means and standard deviations in statistical analysis.

References.

Solutions to Problems.

Statistical Tables.

Index.

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## Author Information

Richard Boddy was a co-founder of Statistics for Industry and has been a Director of the company for 30 years during which time he has lectured on more than 300 courses to scientists and technologists from industry. He has jointly written more than 10 manuals on the use of statistics in Experimental Design, Quality Assurance, Microbiology and Analytical Chemistry among others. He is also co-author of Statistics for Analytical Chemists (Chapman & Hall 1983). He has acted as a consultant to a large number of companies including BP, Glaxo, Ineos, SKF, Chivas, Dupont, BNFL, and British Energy. Previously he was a Chemist with ICI before becoming a Chartered Statistician.

Gordon Smith has always been passionately interested in the practical application of statistics and in the clear communication of it to clients and colleagues in terms which have meaning to them. He was a University research fellow and tutor at Aberdeen University, statistician at the Torry Research Station (part of the then Ministry of Agriculture, Fisheries and Food) where he provided consultancy to scientists of all disciplines in fish technology, collaborating on research papers and providing training in the use of statistics and statistical packages, and director of Statistics for Industry where he developed and presented training courses to scientists and technologists of all disciplines at all level.

Statistics for Industry is a renowned training and consultancy company which was founded in1977 and have trained over 10,000 scientists and technologists in a variety of statistical applications. They have presented courses in Belgium, China, Germany, Ireland, Italy, Hungary, The Netherlands, Nigeria, South Africa, Sweden, Thailand, UK and the USA.

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## Reviews

"Overall, the book could be a clear introduction to a set of useful tools either in self study or used as an aid for instruction for those with no previous exposure." (The American Statistician, 1 February 2011)
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## Related Websites / Extra

An Introduction to Statistics for Scientists and TechnologistsVisit the companion website to access the software examples discussed in the book.
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