The just-about-right pilot sample size to control the error margin (2023)
Journal Article
Obodo, S., Toher, D., & White, P. (2023). The just-about-right pilot sample size to control the error margin. International Journal of Statistics and Probability, 12(3), https://doi.org/10.5539/ijsp.v12n3p1

In practice, the required sample size for a two-arm randomised controlled trial cannot always be determined pre-study with great accuracy. This lack of accuracy has economic, ethical and scientific implications. The sample size for a pilot study is... Read More about The just-about-right pilot sample size to control the error margin.

Estimation of the two-group pilot sample size with a cautionary note on Browne’s formula (2021)
Journal Article
Obodo, S., Toher, D., & White, P. (2021). Estimation of the two-group pilot sample size with a cautionary note on Browne’s formula. Journal of Applied Quantitative Methods, 16(3),

Using data obtained from a pilot study, Browne (1995) proposed a procedure for estimating the sample size needed for a definitive two-arm randomised controlled trial when the minimal important difference is specified. Simulations confirm these findi... Read More about Estimation of the two-group pilot sample size with a cautionary note on Browne’s formula.

Ordinal Logistic Regression as an alternative analysis strategy for the comparison of two independent samples (2021)
Journal Article
Bilski, B., Derrick, B., Toher, D., & White, P. (2021). Ordinal Logistic Regression as an alternative analysis strategy for the comparison of two independent samples. Journal of Applied Quantitative Methods, 16(3),

The two group between subjects design is pervasive with analyses often performed using the Mann Whitney Rank Sum test or using the Welch variant of the t-test. Using simulation it is shown that a dummy variable ordinal logistic regression (OLR) mode... Read More about Ordinal Logistic Regression as an alternative analysis strategy for the comparison of two independent samples.

Investigating Browne's method (2021)
Presentation / Conference
Obodo, S., Toher, D., & White, P. (2021, September). Investigating Browne's method. Poster presented at Statistics at Bristol: Future Reserach and You 2021, Bristol

Results supports Browne’s procedure of pilot sample size determination. However the data reveals that the procedure underestimates and overestimates sample size. Fig. 1 shows 𝛼 and 𝛽 have no practical effect on degree of excess which increases as... Read More about Investigating Browne's method.

Challenge and change: Police identity, morale and goodwill in an age of austerity (2014)
Report
Hoggett, J., Redford, P., Toher, D., & White, P. (2014). Challenge and change: Police identity, morale and goodwill in an age of austerity

One of the largest pieces of independent research on police attitudes in England and Wales. The research, led by Dr James Hoggett from UWE Bristol (the University of the West of England, Bristol), looked at police attitudes to current reform proposal... Read More about Challenge and change: Police identity, morale and goodwill in an age of austerity.

An inverse normal transformation solution for the comparison of two samples that contain both paired observations and independent observations
Journal Article
Derrick, B., White, P., & Toher, D. An inverse normal transformation solution for the comparison of two samples that contain both paired observations and independent observations

Inverse normal transformations applied to the partially overlapping samples t-tests by Derrick et.al. (2017) are considered for their Type I error robustness and power. The inverse normal transformation solutions proposed in this paper are shown to m... Read More about An inverse normal transformation solution for the comparison of two samples that contain both paired observations and independent observations.