1 Introduction

GRBs produce an immense amount of energy ($\approx\!\!\!\! 10^{51}$ergs) which must be emitted by a medium with highly relativistic velocities ($\gamma \gt 100$). Most GRBs are highly variable with a variability scale much smaller than their overall durations and there is considerable debate as to the cause of the variability, which may be due to internal or external shocks (e.g. Sari & Piran 1997; Chiang & Dermer 1997).

GRBs generally have complex time profiles and previous work (McBreen et al. 1994; Hurley et al. 1997) has indicated that some parameters are consistent with lognormal distributions e.g. durations of GRBs. Li & Fenimore (1996) extended the analysis to include BATSE GRBs with multiple peaks and confirmed the applicability of lognormal distributions in GRBs. The results presented here on a large sample of BATSE GRBs were obtained using wavelets. Other techniques have also been used to profile the time structure of GRBs (e.g. Norris et al. 1996; Stern et al. 1996).