Statistics Opportunities

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New Zealand statistics is strong in biosciences such as ecology, biology and genetics. This includes natural populations of animals such as birds; plants and ecologies; fisheries; crop production and animal breeding. It is also strong in graphical displays for statistical information and in earth sciences. In health New Zealand has led the world in aspects of epidemiology, the tracking of health and illness across populations. Survey sampling is strong in certain areas, such as some official statistics, and social issues such as gambling.

The field faces many opportunities. There is a world-wide shortage of survey statisticians, and computing technology is enabling new ways of seeing and animating data, such as animated population pyramids and maps of commuter flows. “The combination of mapping and dynamic graphs is taking off,” says Professor Sharleen Forbes, of Victoria University. Statisticians are also challenged by huge increases in the amount of data available.

IMAges profiles a few of the many statistical developments and applications in Aotearoa.



Testing for cancer
Identifying blocks of genes with highly correlated activity profiles in breast cancer using the PCOT2 methodology developed by Black's former PhD student Dr Sarah Song

Dr Mik Black works with the Cancer Genetics Laboratory at the University of Otago, which is developing gene expression signatures – patterns of genetic activity – to predict outcomes for people with cancer. Scientists examine tumour samples after surgery, and Black uses standard statistical classification methods to predict whether the cancer is likely to come back or not. “Three signatures indicate particularly aggressive cancer, and they have been patented by Pacific Edge Biotechnology,” he says. Clinical trials are the next, very expensive, step to turn those   signatures into diagnostic tests. These take a long time; “we have to wait for five years to see if the cancer comes back. We started six years ago, patented the signatures about four years  ago, but there are a few years to go to get it into hospitals as a working test.” 

“Genetic statistics is most rewarding if we can work closely with clinicians, as they are the people actively caring for patients. Anything we can do that they can translate into improvements for patients - that’s the real reward.”

Census@School

Census@School had its beginnings when Professor Sharleen Forbes convened a group of NZ Statistics Association members in 1990 to run the first children’s census inNew Zealand schools. “We ran it without any money, getting government departments to pay in kind with paper and printers – I wouldn’t ever attempt it again! It was totally voluntary, on top of our day jobs.” “Students wrote about 60,000 reports and six or seven of us gave up our holidays to analyse and feed it back to schools. It was picked up by the Italians and then the Royal Society in the UK developed an internet version.” This became New Zealand’s first Census@School in 2003.

Analysing interactions in natural ecosystems

Statistics is very important in ecology for analysing multiple ecological variables at once, says Professor Marti Anderson of Massey University. “You might walk a transect in a forest, or swim a certain dista
nce underwater and count the individuals of every species you encounter. Each species is a variable and species interact with each other and the environment. One of the challenges is to understand how sets of species change together, either naturally or in response to human-induced changes.” Anderson is pictured with Associate Professor Russell Millar getting ready for a fish biodiversity survey in Northland. She has developed new computer-intensive methods of multivariate analysis for biodiversity and community data. “The biggest problem with ecological variables is they don’t behave like normal Gaussian bellshaped curves, and almost all classical statistical methods are based on that assumption.” She has worked on communities of Antarctic plankton and bacteria, organisms living in sediments in estuaries, butterfly communities in the tropics, marine fish communities in kelp forests, microalgae in freshwater streams, insects collected in pitfall traps, forest communities, and even suites of behavioural chemicals in birds. Her software (PERMANOVA+) enables variation in these complex systems to be partitioned, allowing effects of a disturbance to be assessed against natural variation. It is being used around the world in many ecological applications and environmental impact assessments.

How many possums?

Environmental monitoring drove the development of a simple tool to calculate the population of possums in an area. Associate Professor Jennifer Brown, of Canterbury University, says: “We spend a lot of money trying to control possums, rats and other pests. We want to know the level at which the population impacts on the environment, and whether
we have been effective in managing them. If we have reduced the size of pest populations, are we seeing a gain in conservation?” With Pest Control Research Ltd, her team developed a wax tag that possums can bite and from which they could calculate the surrounding population. “It was revolutionary, compared with the labour-intensive traps we used to use; the tag is now used throughout the country.”
She has also been involved in designing survey protocols to find rare species in their environments. “You can waste a lot of time trying to find rare species,” says Brown. “The survey method seems simple but there is a lot of statistics behind it.” The method has been used to find desmans, a very rare river mole that lives in the Pyrenees in France, as well as in Southland to find invasive weeds before they start spreading.

See Pest Control Research: reports
Pest Control Research: wax tag monitoring
MathsReach interview with Jennifer Brown

Assessing a vaccine

Roughly 200 cases of Meningococcal B were avoided by the MeNZB vaccine between 2004 to 2008, according to a statistical analysis of the vaccine’s effectiveness. Eighty percent of people Image:10statsopportunities Page 2 Image 0001.jpgunder 20 were vaccinated, “a quite remarkable proportion, with the highest coverage in those under five,” says Dr Richard Arnold, of Victoria University. Working with epidemiologists in the Ministry of Health, he used a Poisson regression model to compare vaccinated and unvaccinated populations. The bacterial infection is spread by airborne droplets and is associated with overcrowded households. Infection varies by age, deprivation and ethnicity, so he also controlled for those factors as well as regional, seasonal and yearly variations. “The epidemic had peaked in 2001 and was on its way down naturally when the vaccine was introduced, but we found the vaccine was between 70% and 80% effective in avoiding the disease.”

R + L = ?

Not s
atisfied with a statistical package that has “revolutionised the practice of statistics”, according to the Royal Society of New Zealand, Ross Ihaka, co-creator of R, is working on the next generation, with the working title L. R is a free, open-source, extendable model with the highest hit-rate for mathematical publications in the last decade. It is available from more than 75 websites in more than 30 countries. However, Ihaka (Ngati Kahungunu, Pakeha) says “the world is changing so fast that we desperately need something new now. Data volumes are exploding, and we have no idea as statisticians how to go about analysing petabytes [1,000 terabytes] of data.” His work on L is still theoretical – “you have to get the basics right otherwise you’re constrained by your early decisions” – but shows promise of being thousands of times faster than R.

Indigenous statistical power

In 2002, Te Ropu Rangahau Hauora a Eru Pomare, at the University of Otago, wrote an influential paper about the need for equal explanatory power – the production of information for Maori health and development to at least the same depth and breadth as that obtained for non-Maori. Discussing the NZ Health Monitor surveys by Statistics NZ, Bridget Robson (Ngati Raukawa) argued that good governance “compels us to ensure that data produced by the Crown is at least as productive for Maori as it is for non-Maori”. The simplest method for equal explanatory power is to recruit equal numbers of Maori and non-Maori responders to surveys. Random surveys include approximately 15% Maori and 85% non-Maori, and “will be more likely to meet Pakeha health needs”. The end result is that health surveys “may have the unintentional effect of increasing health disparities”. Robson argued that implementing equal explanatory power in surveys of health and social determinants of health, such as unemployment, “will help to break this cycle of persistent inequalities”.

See Equal Explanatory Power

Tracking rat invaders

Rodent Invasion Project
member Associate Professor Rachel Fewster, of the University of Auckland, is regularly asked by Department of Conservation staff to identify the origin of rats found  around the country. A few years ago she and others obtained genetic profiles for rat populations from many islands around Great Barrier and Stewart Islands, and the Bay of Islands. “Since then they have been eradicated, but new rats have turned up. DOC or the Auckland Regional Council send us a sample and ask us where it came from.” She was able to say recently about two rats from the Bay of Islands that one was almost certainly brought in by boat and the other might have been a swimmer from the mainland. She examines 20 genes from each rat from DNA regions with a lot of variability. “We use microsatellites which don’t code for anything or do any harm if they mutate. In isolated populations, rats will develop their own proportions of those genes. If I get a rat with Gene A, I think it is more likely to come from the island where Gene A is common. We take all 20 pieces of genetic information, and get a fairly clear idea of which island it came from.”

Stats and the senses

Mark Wohl
ers one of 11 statisticians in Plant and Food Research around the country, working with scientists to ensure experiments have the statistical power to determine true treatment effects. For example, he designs and analyses the results of blind tastings by the sensory science teams, which use panels of tasters to assess wine and fruit from New Zealand grapes and orchards. “They might be checking on length of storage or time of picking, or the effect of a different rootstock. Tasters sit in separate booths in front of a computer, ranking up to 15 variables about the taste and smell of the product. “I determine, for example, the presentation order; they may not score the same thing similarly each time because of the tasting order. If they taste  something very sweet first, the next one may be ranked lower. We might use different coloured lights to take away the effect of the colour of the fruit.” “I often use analysis of variance, sometimes multivariate analysis, and principle component analysis with bootstrapping techniques.”

Census and death records

In 1998, death records were the first data set to the linked to the Census in what became the NZ Census-Mortality Study (NZCMS). “At the time,” says NZCMS director Professor Tony Blakely of the University of Otago, “it was probably the biggest example of its kind in the English-speaking world.” The linkage was anonymous and probabilistic, enabling researchers to calculate death rates in  the whole population for the three years after each census from 1981 to 2004. “The NZCMS showed there was a great undercounting of Maori deaths in the 1980s and 90s. There was also little, if any, improvement in Maori mortality rates in the 80s and 90s at a time when non-Maori mortality rates dropped significantly. It’s very tempting to ascribe that to the Rogernomics reforms and resulting high Maori unemployment rates.” The study also showed that relative gaps in mortality between high and low income groups widened in the 1980s and 90s.

See Health Inequalities Research Programme

Statistics on the telly

Dr Richard Arnold was the face of statistics during election night coverage on TVOne in 2008, and he got his predictions “bang on”. His knowledge of the country’s demographics from his time at  Statist
ics New Zealand meant he was able to develop a statistical model to forecast the result. “There is always an early preference for National on election night because the smaller booths that finish counting first tend to be rural, and more likely to go to National.” He adapted and implemented a statistical forecasting method based on matching polling places between elections, which eliminated that early bias. Making sure that the prediction has a reliable margin of error was an important part of the process, because “a prediction without a margin of error is worthless”.