Determining population size

Determining population size

1. Direct Observation

   • Direct observation, also known as observational study, is a method of collecting evaluative information in which the evaluator watches the subject in his or her usual environment without altering that environment
   • Direct observation can be overt, when the subject and individuals in the environment know the purpose of the observation, or covert, when the subject and individuals in the environment are unaware of the purpose of the observation.
   • Structured direct observations are most appropriate when standardized information needs to be gathered, and result in quantitative data. Unstructured direct observation looks at natural occurrence and provides qualitative data, such as that used when administering the Childhood...

2. Indirect Observation

   • is based on data collected by others that is recorded in books, documents, recordings, videos, newspaper articles, etc
   • It largely involves analyzing textual material generated either indirectly from transcriptions of audio recordings of verbal behavior in natural settings
   • Indirect observation is a recent concept in systematic observation. It largely involves analyzing textual material generated either indirectly from transcriptions of audio recordings of verbal behavior in natural settings

3. Sampling

   • Probability Sampling
     • Simple Sampling
     • Systematic Sampling
     • Stratified Sampling
     • Cluster Sampling
     • Area Sampling
     • Multi-Stage Sampling
   • Non-Probability Sampling
     • Judgement Sampling
     • Convenience Sampling
     • Quota Sampling
     • Snowball Sampling

4. Mark and recapture

   • Mark and recapture is a method commonly used in ecology to estimate an animal population's size where it is impractical to count every individual.
   • A portion of the population is captured, marked, and released. Later, another portion will be captured and the number of marked individuals within the sample is counted.
   • Since the number of marked individuals within the second sample should be proportional to the number of marked individuals in the whole population, an estimate of the total population size can be obtained by dividing the number of marked individuals by the proportion of marked individuals in the second sample