Generally, biodiversity simply means the number of species in a natural place, but it has a deeper meaning too. To understand the inner meaning of the term biodiversity we have to take into account the two main factors richness and evenness. Biological diversity can be quantified in many different ways. Some of the usual indices of biodiversity are Simpson’s index, Shannon index, etc. All these conventional indices measure biodiversity based on sampled data and no utilization of such sampling methods have been considered while computing the indices. In this study we have tried to impose the concept of detectability and sampling in these usual biodiversity indices.

We, in our study first have introduced detectability in the usual indices in a way that, on the basis of population types we have considered some specific sampling methods and have estimated the population total. Then with these estimated population total we have tried to find out the affect of introducing detectability on these usual indices. To figure out the effect of this new approach we have collected data on plant species by the line transect method and fish species data by the capture-recapture method from Curzon Hall, University of Dhaka Campus. Significant difference and comparison of the two approaches were then viewed with the help of bar-diagram and dendogram. Finally, we have tried to draw a valid conclusion: detectability should be considered while measuring biodiversity and have suggested some guidelines for further research on the same field.