Oliver Stevenson

PhD Candidate | Department of Statistics | University of Auckland

 

Hello!

I am a PhD candidate in the Department of Statistics at the University of Auckland where I spend my time investigating statistical models that can be utlised in the field of sports analytics. My current research involves the development and implementation of various machine learning algorithms that can be applied to the sport of cricket, primarily to estimate and predict the past, present and future abilities of professional cricketers.

I also provide statistical and data consulting services to those looking for help with data modelling, data analysis and other data-related questions. I have advised clients who work in a range of fields including IT, market research, clinical trials and sports analytics, and I’m always up for a new challenge.

Feel free to take a look at my past and present research below, or get in touch if you have any questions regarding statistics, data, cricket or otherwise.

Research

Research interests:

  • Sports analytics
  • Bayesian inference
  • Machine learning
  • Computational statistics

Doctor of Philosophy (2017 - present)

Since mid-2017, I have been studying towards a Doctor of Philosophy under the supervision of Dr Brendon Brewer. Following on from my Masters, my research has involved developing a range of statistical models that can be applied to the analysis of sporting data, with a particular focus on cricket. As with any sport or profession, we shouldn’t expect a player to perform with some constant ability throughout their entire career. Instead, we are likely to observe both short and long-term variations and fluctuations in ability due to the likes of age, experience, fitness and general improvements or deteriorations in technique.

Therefore, I have implemented a range of models that use machine learning algorithms to better estimate and predict the past, present and future batting and bowling abilities of professional cricketers. When estimating current player ability, the models account for a range of external factors, including recent form, strength of opposition and venue of past performances (e.g. home or away). These estimates have been proven to provide more accurate predictions of player peformance compared with traditional cricketing metrics, such as batting and bowling averages. Additionally, the models have the benefit of maintaining an intuitive cricketing interpretation, unlike other popular ranking metrics, such as the official ICC rankings. Given two proposed playing XIs, we can use the estimated player abilities to provide a percentage prediction of each team winning a match.

See below for an overview of my current Test batting rankings, including an interactive application that allows users to visualise the batting career trajectories of international cricketers.

Master of Science (2016 - 2017)

In 2017 I completed my Masters degree under the supervision of Dr Brendon Brewer. My research looked to tell a more meaningful story behind a cricket player’s batting average. Using Bayesian statistical techniques, I explored more in-depth methods of quantifying a cricketer’s batting ability than the simple batting average. More specifically, I built statistical models which estimate how well a batsman is playing at any given point in their innings, allowing us to quantify the cricketing concept of a batsman ‘getting their eye-in’. The primary focus was on Test match cricket, with wider applications to 4-day First Class cricket. Using these models, I also explored the plausibility of popular cricketing superstitions from a statistical point of view, such as the commentator’s favourite, the ‘nervous 90s’.

ABSTRACT: Cricketing knowledge tells us batting is more difficult early in a player’s innings, but gets easier as a player becomes familiar with the local conditions. Using Bayesian inference and nested sampling techniques, a model is developed to predict the Test match batting abilities of international cricketers. The model allows for the quantification of players’ initial and equilibrium batting abilities, and the rate of transition between the two. Implementing the model using a hierarchical structure provides more general inference concerning a selected group of international opening batsmen from New Zealand. More complex models are then developed, which are used to identify the presence of any score-based variation in batting ability among a group of modern-day, world-class batsmen. Additionally, the models are used to explore the plausibility of popular cricketing superstitions, such as the ‘nervous 90s’. Evidence is found to support the existence of score-based variation in batting ability, however there is little support to confirm a widespread presence of the ‘nervous 90s’ affecting player batting ability. Practical implications of the findings are discussed in the context of specific match scenarios.

Click here to read thesis titled “The nervous 90s: a Bayesian analysis of batting in Test cricket”.

Bachelor of Science (Honours) (2015)

ABSTRACT: At a glance, data is more meaningful when presented in graphical form. This project explored innovative methods of automating the display of catch data for large-scale conservation projects. High priority was given to developing methods that allow users to interact with their data, affording them some control over the graphics that are produced. Two interactive applications were developed that allow conservation volunteers to select the data they want to view and how to view it. After a day in the field, volunteers are able to use these applications to see their day’s work summarised on a map or graphic. These graphics highlight the positive impact their efforts are having on the local environment, keeping volunteers motivated and engaged in their work. Various methods of improving the automation of these graphics are outlined, as well as other practical uses of these statistical applications.

Click here to read dissertation titled “Graphical applications for large-scale conservation projects”.

Last updated 2nd September 2020.

Players must have participated in a Test match since 2019 and must have batted in a minimum of 15 Test innings to be ranked.

RankPlayerCountryInningsRunsCareer averagePredicted averageICC rating (#)
1Steve SmithAUS131722762.857.9911 (1)
2Marnus LabuschagneAUS23145963.455.8827 (3)
3Babar AzamPAK53204545.453.6797 (5)
4Virat KohliIND145724053.651.4886 (2)
5David WarnerAUS155724448.947.9793 (6)
6Kane WilliamsonNZ140647651.047.8812 (4)
7Angelo MathewsSL154598145.347.5658 (17)
8Rohit SharmaIND53214146.546.6674 (16)
9Mayank AgarwalIND1797457.346.2714 (11)
10Joe RootENG177782348.045.8738 (9)
11Ross TaylorNZ178723846.143.5677 (15)
12Cheteshwar PujaraIND128584048.743.4766 (7)
13Azhar AliPAK152612942.942.7627 (23)
14Ajinkya RahaneIND109420342.941.7726 (10)
15Tom LathamNZ92372642.340.8710 (12)
16Mushfiqur RahimBAN130441336.840.4654 (18)
17Ben StokesENG122442837.839.4760 (8)
18Dinesh ChandimalSL103387740.839.3563 (38)
19Travis HeadAUS28109142.038.1643 (20)
20BJ WatlingNZ110365838.538.1621 (25)
21Shakib Al HasanBAN105386239.438.0NA
22Tamim IqbalBAN115440538.638.0597 (31)
23Rishabh PantIND2281438.837.8555 (42)
24Henry NichollsNZ50174739.737.7652 (19)
25Usman KhawajaAUS77288740.737.7584 (35)
26Asad ShafiqPAK128466038.237.7608 (26)
27Kusal MendisSL85299537.037.6628 (22)
28Dimuth KarunaratneSL128452436.837.2680 (14)
29Dominic SibleyENG1968638.136.5567 (37)
30Faf du PlessisSA112390139.836.2586 (34)
31Ravindra JadejaIND71186935.335.7551 (44)
32Brendan TaylorZIM62205535.435.4599 (30)
33Dean ElgarSA110388838.535.3624 (24)
34Darren BravoWI98350637.735.0448 (71)
35Joe BurnsAUS36137938.335.0491 (60)
36Sean WilliamsZIM2477033.535.0480 (66)
37Quinton de KockSA80293439.135.0706 (13)
38Craig ErvineZIM36120835.535.0549 (45)
39Mominul HaqueBAN74286040.934.5556 (41)
40Jos ButtlerENG82254333.934.2637 (21)
41Soumya SarkarBAN74286040.934.1421 (76)
42Matthew WadeAUS55144031.334.1488 (61)
43KL RahulIND60200634.634.0504 (55)
44Colin de GrandhommeNZ36118537.034.0589 (33)
45Peter HandscombAUS2993438.933.9NA
46Sikandar RazaZIM30103734.633.6487 (62)
47Dhananjaya de SilvaSL57186335.233.4561 (39)
48Roshen SilvaSL2370235.132.7NA
49Shan MasoodPAK43136831.832.3600 (29)
50Jermaine BlackwoodWI55157330.832.2494 (57)
51Rory BurnsENG38123332.432.2597 (31)
52Jason HolderWI75201231.932.1553 (43)
53Hanuma VihariIND1655236.831.8529 (47)
54Sarfraz AhmedPAK86265736.431.5NA
55MahmudullahBAN93276431.831.5514 (51)
56Niroshan DickwellaSL66192131.031.4578 (36)
57Ollie PopeENG2064537.931.1531 (46)
58Haris SohailPAK2381937.230.8480 (66)
59Tim PaineAUS50133031.730.6516 (50)
60Roston ChaseWI64185230.929.8508 (53)
61Joe DenlyENG2882729.529.7520 (49)
62Shaun MarshAUS68226534.329.5NA
63James PattinsonAUS2541726.129.1NA
64Kusal PereraSL3393431.128.9481 (65)
65Shane DowrichWI62157029.128.1521 (48)
66Kraigg BrathwaiteWI118367233.128.0514 (51)
67Temba BavumaSA67184530.827.8485 (64)
68Jonny BairstowENG123403034.727.5486 (63)
69Wriddhiman SahaIND50123830.227.5388 (82)
70Shimron HetmyerWI3083827.927.4505 (54)
71Liton DasBAN3485926.026.6450 (70)
72Chris WoakesENG60132127.526.4404 (78)
73Cameron BancroftAUS1844626.226.3368 (90)
74Sam CurranENG3172827.026.2440 (73)
75Aiden MarkramSA37142438.525.5608 (26)
76Mitchell SantnerNZ2974125.625.4380 (84)
77Regis ChakabvaZIM3480625.224.8337 (94)
78Imam ul-HaqPAK2148525.524.5367 (91)
79Keaton JenningsENG3278125.224.3NA
80Jeet RavalNZ39114330.124.1456 (68)
81Mitchell MarshAUS55126025.223.8371 (89)
82John CampbellWI1838225.523.6396 (81)
83Ravichandran AshwinIND98238928.123.5372 (88)
84Mitchell StarcAUS85151522.322.8375 (86)
85Shai HopeWI64160326.322.6454 (69)
86Lahiru ThirimanneSL68140422.622.6329 (96)
87Moeen AliENG104278229.021.9358 (92)
88Adil RashidENG3354019.321.2NA
89Theunis de BruynSA2342819.520.9317 (99)
90Jack LeachENG1822018.320.4NA
91Matt HenryNZ1622418.720.4NA
92Marcus HarrisAUS1738524.120.1323 (98)
93Mohammad MithunBAN1630819.219.8NA
94Mark WoodENG2839918.119.5NA
95Trent BoultNZ8265415.218.3NA
96Mehidy HasanBAN4263817.718.2NA
97Donald TiripanoZIM2029919.918.1NA
98Tim SoutheeNZ106166817.417.8NA
99Keshav MaharajSA4864315.317.6NA
100Imrul KayesBAN76179724.317.4333 (95)

 

The batting rankings are based on the models developed as part of my Masters and PhD at the University of Auckland. More detail about these models can be found in the papers I have published, which can be found in the Publications section below.

When estimating a player’s current ability the model accounts for recent form, venue of matches played in (i.e. home, away or neutral) and whether the player was batting in their team’s first or second innings of the match. Additionally, the model accounts for the “getting your eye in” process for each individual player. The data support the general belief that players tend to score more runs when batting in their team’s first innings of a match, at a home venue.

The “predicted average” is the the number of runs we expect the player to score in their next Test innings, assuming their next innings is played at a neutral venue and it is unknown whether they are batting in their team’s first or second innings of the match. The official International Cricket Council (ICC) ratings (and world ranking #) are also provided for comparison. The ranking of players is generally similar between the two methods, although there are a couple of notable differences.

Firstly, our model rewards players who are able to overcome the “getting your eye in” process and remain on a not out score, while the ICC ratings simply provide not out innings with a “bonus” that we susepct is too low. For example, Rohit Sharma has a number of 50+ not out scores, suggesting he frequently overcomes the difficult “getting your eye in” process, but for various reasons, has not had the opportunities to convert these not out innings into big scores.

Secondly, the ICC ratings tend to place more emphasis on recent innings compared with our models. Our general findings suggest that there is little evidence to suggest that recent form is a significant predictor of current batting ability for the majority of players. Instead, we believe a player’s underlying ability tends to change slowly over time, rather than erratically between innings as a direct result of recent performances. It is unclear whether the ICC ratings attempt to provide predictive accuracy of ability, or instead tries to formalise expert judgement about who is in and out of form. These two goals may not be entirely compatible.

Thirdly, the ICC apply a rating decay system, whereby players who have not batted in a recent match, see their rating slowly
decline. While well intentioned to reflect the best current batsmen in the world, the decay system is inherently biased as it tends to affect smaller nations disproportionately, who are generally afforded fewer opportunities to play Test cricket.

Finally, while both methods provide a general indication of batting ability, by measuring underlying batting ability in units of a batting average, rather than arbitrary “rating points”, we are able to maintain an intuitive cricketing interpretation when comparing players. Instead of concluding “Steve Smith is 99 rating points better than Kane Williamson”, we can make more meaningful probabilistic statements, such as “we expect Steve Smith to outscore Kane Williamson by 10 runs in their next respective innings”, or “we expect Steve Smith has a 59.9% chance of outscoring Kane Williamson in their next respective innings”. In both statements we are assuming a neutral venue and it is unknown whether they are batting in their team’s first or second innings of the match. Of course, we can update these estimates to include match-specific information, if we know the venue of the next match and whether the player is batting in their team’s first or second innings of the match.

Here you can find an application that allows users to visualise how the models estimate batting ability on two scales:

1. Short-term changes in ability that occur during an innings due to the “getting your eye in” process

2. Long-term changes in ability that occur between innings, over a playing career, providing an estimate of a player’s batting career trajectory to date, as well as a prediction for their current and future ability. These estimates are what are used to compute our batting rankings.

Publications

Stevenson, O. G., & Brewer, B. J. Finding your feet: a Gaussian process model for estimating the abilities of batsmen in Test cricket. Submitted to Journal of the Royal Statistical Society: Series C (Applied Statistics). Preprint.

Stevenson, O. G., & Brewer, B. J. (2018). Modelling career trajectories of cricket players using Gaussian processes. In R. Argiento, D. Durante, & S. Wade (Eds.), Bayesian Statistics and New Generations: Proceedings of the 2018 Bayesian Young Statisticians Meeting (pp. 165-173). Springer, Cham. Preprint.

Stevenson, O. G., & Brewer, B. J. (2017). Bayesian survival analysis of batsmen in Test cricket. Journal of Quantitative Analysis in Sports13(1), 25-36. Preprint.

Stevenson, O. G. (2017). The Nervous 90s: A Bayesian Analysis of Batting in Test Cricket. Masters thesis, University of Auckland. Online version.

Blog & News

Contact

o.stevenson@auckland.ac.nz

University of Auckland | Department of Statistics | Room 303S.376