ANALYZING ROAD-SIDE BREATH TEST DATA

GROUP MEMBERS

• Micheal Abaho• Yogesh Shinde• Natasha Thakur• Mingyang Chen• Huw Fulcher• Kai Wang

OBJECTIVE

• To understand how attributes explain intoxication in pulled over drivers

• Analyze the dataset• Determine what attributes to classify intoxication with• Perform classification using dataset• Assess success of classification in explaining

intoxication

DATASET

• Acquired from data.gov.uk• 2014 data on roadside breath

tests• Approximately 300,000

records

• Reason for test• Suspicion of Alcohol, Road Traffic Collision, Moving Traffic Violation and Other

• Month • Jan to Dec

• Year• 2014

• Week Type:• Weekday and Weekend

• Time Band• 12am-4am, 12pm-4pm, 4am-8am, 4pm-8pm, 8am-12pm, 8pm-12am and Unknown

• Age Band for Drivers• 16-19, 20-24, 25-29, 30-39, 40-49, 50-59, 60-69, 70-98 and Other

• Gender for Drivers• Male and Female

• Breath Alcohol Level

ATTRIBUTES

EXPLORATORY ANALYSIS

PRE-PROCESSING DATA

• Removing year• Removing outliers

• Creating decision variable

REASON*

Intoxicated = 0.0735 * Reason=Suspicion of Alcohol + 0.0365 * Reason=Other +-0.0428 * Reason=Moving Traffic Violation + 0.1132

MONTH

Intoxicated = -0.0453 * Month=Jan + -0.0224 * Month=Feb + -0.0173 * Month=Mar + -0.0147 * Month=Apr + -0.0086 * Month=May + -0.0952 * Month=Jun + -0.0189 * Month=Jul + -0.013 * Month=Sep + -0.0179 * Month=Oct + -0.0295 * Month=Nov + -0.1249 * Month=Dec + 0.1669

WEEKTYPE

TIMEBAND*

Intoxicated = 0.1009 * TimeBand=12am-4am + 0.0733 * TimeBand=4am-8am + -0.0368 * TimeBand=4pm-8pm + -0.0539 * TimeBand=12pm-4pm + -0.0598 * TimeBand=8am-12pm + 0.118

AGE* + GENDER*

CLASSIFICATION OF THE DATASET

EVALUATION MEASURE

• A classifier predicts all data instances of a dataset as either positive or negative.

• This classification (or prediction) produces four outcomes – true positive, true negative, false positive and false negative.

WHAT IS TP,FP,FN,TN?

• True Positive (TP) – It is an instance which is correctly predicted to belong to class.• True Negative (TN) – It is an instance which is correctly

predicted to not belong to class.• False Positive (FP) – It is an instance which is

incorrectly predicted to belong to class.• False Negative (FN) – It is an instance which is

incorrectly predicted to not belong to class.

CONFUSION MATRIX

• A confusion matrix is a two by two table formed by counting of the number of the four outcomes of a classifier that is TP, FP, TN, FN.

Predicted

Class A

Class B <- classified as

Observed

TP FN Class A

FP TN Class B

MEASURES FROM THE CONFUSION MATRIX

• Error rate (ERR) is calculated as the number of all incorrect predictions divided by the total number of the dataset.

• The best error rate is 0.0, whereas the worst is 1.0.

• Accuracy (ACC) is calculated as the number of all correct predictions divided by the total number of the dataset.

• The best accuracy is 1.0, whereas the worst is 0.0.

• True positive rate (TPR) is calculated as the number of correct positive predictions divided by the total number of positives.

• The best sensitivity is 1.0, whereas the worst is 0.0.

• False positive rate (FPR) is calculated as the number of incorrect negative predictions divided by the total number of negatives.

• The best false positive rate is 0.0 whereas the worst is 1.0.

• Precision (PREC) is calculated as the number of correct positive predictions divided by the total number of positive predictions.

• The best precision is 1.0, whereas the worst is 0.0.

• Recall is proportion of actual positives that were predicted positive.

• F-measure is a harmonic mean of precision and recall.

J48

• J48 is the improved version of C4.5

• C4.5 is a program that creates a decision tree based on a set of labelled input data.

• First it constructs a very huge tree by considering all attribute values and narrow down the decision rule with the help of pruning.

• Pruning reduces the size of decision trees by removing sections of the tree that provide little power to classify instances.

• Information gain or entropy measure is used to get the best attribute to split the Nodes.

• A tree structure is created with root node, intermediate and leaf nodes, where Node

holds the decision and in turn decision helps to achieve our result.

CLASSIFICATION BASED ON TREES (J48)

• Attributes: Reasons, AgeBand, TimeBand,

Gender• Object: Driver• Class: Yes/No for intoxication.• Test Mode:10 Fold Cross Validation• Pruned Tree

EXPERIMENT WORK AND OUTCOME

Summary

J48:Pruned Tree

Number of Leaves :1Size of the tree :1

No (323555.0/37379.0)

J48 CLASSIFICATION OUTPUT

Confusion Matrix Predicted

Actual

Detailed Accuracy By Class

JRIP

RULE BASED CLASSIFICATION (JRIP)

Decision Tree and Decision Table(classify rule)

RULE BASED CLASSIFICATION (JRIP)

• Repeated Incremental Pruning to Produce Error Reduction (RIPPER)•Optimized version of IREP (reduced error pruning) a very common and effective technique found in decision tree algorithms

RULE BASED CLASSIFICATION (JRIP)

• The training data is split into a growing set and a pruning set

• Growing set: greedily adding conditions until the rule is perfect

• pruning set: delete conditions until find better rule• Rule set generate by growing rule and pruning rule• Optimization stage

RULE OF JRIP

PERFORMANCE OF JRIP

COMPARE WITH J48

WHICH CLASSIFICATION ALGORITHM?

•Accuracy of Classifier Both J48 and JRip for our case is high •Speed: Time 4.26s in JRip; 1.14 in J48•Robustness：Noisy data/missing data•Scalability： Size of dataset becomes big

REGRESSION

WHAT IT IS AND WHAT IT DOES Determines how a dependent variable is affected by one or more independent

variables.Dependent variable:- Is a result or something that is being predicted.Independent variable: Predictor.

Regression Equation (In its simplicity)Y = a + bX +

[ Y – (Dependent variable), X – (Ind variable)Expected value of )

Aim is to ensure you find values of a and b such that e is small

THE REGRESSION MODEL DERIVED

y

- error

a - intercept

X

𝑦=𝑎+𝑏𝑥+𝑒

LOGISTIC REGRESSION

Why this regression

1. Predictive analysis of a dichotomous dependent variable.• E.g. for our case we are building a model that predicts whether

some one is intoxicated or not. i.e. what do factors like violating traffic rules, age-band and time band tell us about the probability that a person is intoxicated or not when they’re stopped by police.

2. We discover additional trends in data without having to run other tests how each of the predictors affects the resultant dependent variable.

RESULTS AND EVALUATION – REGRESSION MODEL

No Yes Precision

Recall

F-Measure

ROC Area

No 285403

773 0.885 0.997

0.938 0.726

Yes 36923 456 0.371 0.012

0.024 0.726

Weighted Average

0.826 0.883

0.832 0.726

Classified/Predicted

Actual

Correctly Classified Instances

285859 88.3494 %

Incorrectly Classified Instances

37696 11.6506 %

Mean absolute error 0.1886Root mean squared error

0.3075

Relative absolute error 92.2893 %Root relative squared error

96.1835 %

Total Number of Instances

323555

Attribute Coefficients OddsReason=Suspicion of Alcohol -0.486 0.6151Reason=Moving Traffic Violation 0.5511 1.7352TimeBand=12am-4am -0.849 0.4278TimeBand=4am-8am -0.6143 0.541TimeBand=8am-12pm 0.6492 1.914AgeBand=16-19 0.1976 1.2184AgeBand=25-29 -0.2082 0.8121AgeBand=70-98 0.86 2.3632Gender=Male -0.1297 0.8784Gender=Female 0.1268 1.1352Intercept 2.3189

From = a + bX = 2.3189 – 0.486*(Sus_Alc) + 0.5511*(Mov_Traf) – 0.849 * (Timeband) + …………………………..

Regression equation predicting whether some one is intoxicated or not.

CONCLUSION

CONCLUSION/WHAT WE DISCOVERED

• Four “optimal” attributes to use in classification• J48 – Performs well but not practical• JRip – Most accurate (Not by much) but needs

tweaking• Regression – “Best” of the 3

CONCLUSION / RECOMMENDATION

• Test the data set for more assumptions – Normality, Multi-collinearity,• and Homoscedasticity.• Transform the dataset to minimize the errors

generated from the biased number of cases belonging to class (No – None intoxication).• Explore further experiments including other

factors that are potential predictors of intoxication. e.g Offences (How offensive is a person when asked to pull-over by police).