[...]... Stillbirth Termination of pregnancy Total < 25 No % 94 74Á0 21 16Á5 10 7Á9 2 1 6 0 0Á0 12 7 10 0Á0 25±29 No % 962 70Á3 272 19 Á9 96 7Á0 36 2Á6 2 0 1 1368 99Á9 30±34 No % 16 15 71 7 430 19 1 143 6Á3 58 2Á6 8 0Á4 2254 10 0 1 35±39 No % 789 64Á4 338 27Á6 66 5Á4 27 2Á2 6 0Á5 12 26 10 0 1 40 ‡ No % 69 48Á9 60 42Á6 6 4Á3 1 0Á7 5 3Á5 14 1 10 0Á0 Total No % 3529 69Á0 11 21 21 9 3 21 6Á3 12 4 2Á4 21 0Á4 511 6 10 0Á0 resulted in a... virus in egg membranes Number of lesions Frequency (number of membranes) Relative frequency (%) 0± 10 ± 20± 30± 40± 50± 60± 70± 80± 90± 10 0± 11 0 11 9 1 6 14 14 17 8 9 3 6 1 0 1 1 8 18 18 21 10 11 4 8 1 0 1 Total 80 10 1 Quantitative variables are those for which the individual observations are numerical quantities, usually either measurements or counts It is useful to subdivide quantitative observations into... result of adding 10 1 (accurate to the nearest integer) and 4Á39 (accurate to two decimal points) is 10 5 (to the nearest integer) The last digit may be in error by one unit; for example, the exact figure corresponding to 10 1 may have been 10 1Á42, in which case the result of the addition now should have been 10 5Á 81, or 10 6 to the nearest integer These considerations are particularly important in subtraction... origin should be indicated by a break in the axis at the 10 Describing data 1 4 weeks Under 1 week Under 1 week Under 1 week 1 4 weeks 1 4 we eks 4 weeks 1 year 19 47 4 weeks 1 year 4 weeks 1 year 19 67 19 86 Fig 2.2 A pie chart showing for three different years the proportions of infant deaths in England and Wales that occur in different parts of the first year of life The amount for each category is... quite different investigations in which statistical methods played an essential part 1 MacKie et al (19 92) studied the trend in the incidence of primary cutaneous malignant melanoma in Scotland during the period 19 79±89 In assessing trends of this sort it is important to take account of such factors as changes in standards of diagnosis and in definition of disease categories, changes in the pattern... formulae and, more particularly, the concepts behind them Even the more advanced methods described in this edition are being extensively used in medical research and they find their way into the reports subsequently published in the medical press It is important that the medical research worker should understand the gist of these methods, even though the technical details may remain something of a mystery... interferenceÐthe death of the animalÐand the non -statistical techniques are more akin to those of a laboratory experiment than to those required in most survey work The general principles of experimental design will be discussed in §9 .1, and those of survey design in § 19 .2 and 19 .4 2 Describing data 2 .1 Diagrams One of the principal methods of displaying statistical information is the use of diagrams Trends... conception (AIH National Perinatal Statistics Unit, 19 91) , is an example of a table summarizing counts It summarizes information on 511 6 women who conceived following in vitro fertilization (IVF), and shows that the proportion of women whose pregnancy 12 Describing data Table 2 .1 Outcome of pregnancies according to maternal age (adapted from AIH National Perinatal Statistics Unit, 19 91) Age Live birth Spontaneous... distinction is sometimes hard to draw Consider, for instance, the following series of statistical studies: 1 A register of deaths occurring during a particular year, classified by the cause of death 2 A survey of the types of motor vehicle passing a checkpoint during a certain period 3 A public opinion poll 4 A study of the respiratory function (as measured by various tests) of men working in a certain... the data about the issues under research Both these developments, of planning and inference, owe much to the work of R.A (later Sir Ronald) Fisher (18 90 19 62), whose influence is apparent throughout modern statistical practice Almost all the techniques described in this book can be used in a wide variety of branches of medical research, and indeed frequently in the non -medical sciences also To set the . 306 11 Modelling continuous data, 312 11 .1 Analysis of variance applied to regression, 312 11 .2 Errors in both variables, 317 11 .3 Straight lines through the origin, 320 11 .4 Regression in groups,. 698 19 .11 Intraclass correlation, 704 19 .12 Disease screening, 707 19 .13 Disease clustering, 711 20 Laboratory assays, 717 20 .1 Biological assay, 717 20.2 Parallel-line assays, 719 20.3 Slope-ratio. Patents Act 19 88, without the prior permission of the publisher. First published 19 71 Reprinted 19 73, 19 74, 19 77, 19 80, 19 83, 19 85 Second edition 19 87 Reprinted 19 88 (twice), 19 90, 19 91, 19 93 Thrid