INTRODUCTION TO STATISTICAL MODELLING IN R

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P.M.E.Altham, University of Cambridge 3733 40 1835 85 4337 90 5439 50 3341 80 6043 65 51Fitting a logistic modelFitted Probability of failure0.2 0.4 0.6 0.820 30 40 50LoadFigure 7.1: An example of a logistic curve
Chapter 8The space shuttle temperaturedata: a cautionary taleThis is an example on logistic regression and safety in space.Swan and Rigby (GLIM Newsletter no 24,1995) discuss the data below, using binomiallogistic regression. To quote from Swan and Rigby‘In 1986 the NASA space shuttle Challenger exploded shortly after it was launched.After an investigation it was concluded that this had occurred as a result of an ‘O’ring failure. ‘O’ rings are toroidal seals and in the shuttles six are used to preventhot gases escaping and coming into contact with fuel supply lines.Data had been collected from 23 previous shuttle flights on the ambient temperatureat the launch and the number of ‘O’ rings, out of the six, that were damaged duringthe launch. NASA staff analysed the data to assess whether the risk of ‘O’ ringfailure damage was related to temperature, but it is reported that they excludedthe zero responses (ie, none of the rings damaged) because they believed them to beuninformative. The resulting analysis led them to believe that the risk of damagewas independent of the ambient temperature at the launch. The temperatures forthe 23 previous launches ranged from 53 to 81 degreees Fahrenheit while the Challengerlaunch temperature was 31 degrees Fahrenheit (ie, -0.6 degrees Centigrade).’Calculate pfail = nfail/six, wheresix 0))#note that here we are picking out a subset by using the ‘logical condition’#(nfail>0). Alternatively, for this example we could have used the condition38
Page 1: INTRODUCTION TO STATISTICALMODELLIN
Page 4 and 5: PrefaceR is available as Free Softw
Page 6: Chapter 1Getting started: books and
Page 9: Chapter 2Ways of reading in data, t
Page 13 and 14: P.M.E.Altham, University of Cambrid
Page 29 and 30: Chapter 5A 2-way anova, how to set
Page 33 and 34: Chapter 6A 2-way layout with missin
Page 37: P.M.E.Altham, University of Cambrid
Page 59 and 60: Chapter 12Fisher’s exact test, 3-
Page 63 and 64: Chapter 13Defining a function in R,
Page 65 and 66: zbP.M.E.Altham, University of Cambr
Page 83 and 84: Chapter 18Crime and unemployment: a
Page 87 and 88: Chapter 19Maximising a multi-parame
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Chapter 22Brief introduction to Sur
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IndexAIC, 36.Rdata, 10.Rhistory, 10
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INTRODUCTION TO STATISTICAL MODELLING IN R

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