Mathematical and Statistical Consulting Services

Short-term Statistical Analyses

For students, researchers, faculty and administrators at NIU, we provide advice and assistance with short-term statistical analyses. This includes help with designing experiments, clinical trials, observational studies and surveys, as well as analyzing data and interpreting the results. You are especially encouraged to contact us early in your research, preferably at the design stage. The time typically required to complete a project varies from a few hours to several weeks.

Long-term Collaborative Research

We seek to promote cross-disciplinary relationships and collaborative research between the faculty within the School of Mathematical and Statistical Sciences and their counterparts working in other disciplines throughout the university. If you are engaged in a project that is suitable for collaborative research, please contact the director of the MSCS at statconsult@niu.edu.

Assistance in Preparation of Research Grant Proposals

We invite researchers preparing grant proposals to include statistical consulting and data analyses as items in research plans and budgets. The director of the MSCS is available for help in preparing budget estimates and for advice in writing statistical sections of research proposals.

If you are seeking our advice on designs and analyses of your study, please bring the following:

• An abstract of your proposal and/or a clear statement of purpose for your project
• A list of research questions you want to answer
• Copies of relevant articles and earlier work on similar topics in your discipline

If you are seeking our advice on data analyses or report writing after gathering your data, please bring the following in addition to the items above:

• A copy of the experimental protocol
• A sample datasheet
• An electronic copy of the complete data set (Microsoft Excel format is acceptable)
• Results of any preliminary analyses performed

At this point, our resources permit us to perform data analyses using SAS, SPSS and R programming environments. We can also advise clients should they choose to perform their own statistical analyses using alternative software.

Initial Meeting

For the first meeting between clients and our MSCS consultants, we charge a nominal fee of $50 for NIU students and $100 for all others.

Extended Services

Clients are charged hourly fees for services beyond the first meeting. Our current fee schedule is as follows:

• Individual clients or clients from private entities are charged $80 per hour for work done by Ph.D. student consultants and $200 per hour for work done by the director. Code release fee is negotiable.
• Clients from NIU, government or non-profit entities are charged $60 per hour for work done by Ph.D. student consultants and $160 per hour for work done by the director. No code release fee.

Sponsored Research

Clients who engage in sponsored research are encouraged to include statistical consulting in their proposals. This can take the form of a direct-cost line item, a partial or full graduate assistantship, or partial funding of a faculty member.

Collaboration

If the project calls for a standard statistical design and analyses, then co-authorship with us is usually not appropriate. If the project involves nonstandard statistical techniques, then co-authorship is encouraged.

Categorical Data Analysis

The study investigated the potential benefits and risks of the use of non-vitamin and non-mineral (NVNM) supplements. The following research questions were analyzed: (1) whether there are associations between the use of NVNM supplements and the income level and the ethnic background; (2) whether NVNM supplement users with certain medical condition alert a health care professional. All data are categorical. To answer these questions, contingency tables were constructed and Fisher's exact tests were used to test whether the associations are significant. The logistic regression models were built to adjust for other covariates to validate the significance of the associations.

Analysis of Variance

The purpose of the experiment was to determine if core strength is correlated to running speed in high school athletes. In the study, one group of athletes was exposed to a core strengthening program and one control group was not. The pre- and post-test measurements were taken from each group. The data on confounding variables were also collected. An analysis of covariance model was used to determine the effect of the core strengthening program while controlling for the confounders.

Regression Analysis

The research objective was to assess the influence of personality hardiness, stress and psychological resource on career transition outcomes, in particular, the length of time it takes to complete the transition. The personality hardiness, stress and psychological resource are measured by standard instruments from the existing literature. These instruments were validated in the analysis. The response variable was appropriately transformed such that it was approximately normally distributed. The linear regression model was built to assess the effects of the above three factors while adjusting for other relevant covariates.

Linear Mixed Model

The goal of the study was to determine whether the consolidation of Illinois school districts resulted in a change in the discipline practices. The discipline practices were measured by the expenditure, transportation cost and students' reading and mathematics scores. They were measured repeatedly for several years from each school district before and after consolidation. To account for the correlation of measurements within each school district and other factors that might affect these measurements, the linear mixed model was adopted to determine whether there was a significant impact of consolidation on these discipline practices.

Non-linear Mixed Model

The project analyzed the maternal care of two species of monkey: Callimico goeldii and Callithrix jacchus. Callimico goeldii gives birth to single offspring while Callithrix jacchus gives birth to twins. It was conjectured that Callimico goeldii, with its single births, has shifted its maternal care to increase behavioral care and the amount of time dedicated to infant care relative to Callithrix jacchus. This study measured a variety of maternal care to confirm this hypothesis. Each subject in the study was measured repeatedly for several weeks and the response variables are count data. The non-linear mixed models were applied on the data to establish whether the two species are different in terms of maternal care or not.