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Biostatistics

Question
17 out of 76
 

People were separated into 5 sub groups. People were selected randomly from these sub groups. What type of sampling was done?


A Simple random sampling
B Stratified sampling
C Cluster sampling
D Systematic sampling

Ans. B Stratified sampling
Sampling

Sampling technique in which the population is first divided into sub groups or strata and then sample is chosen randomly from each strata is known as stratified random sampling.

It is used when the population is:

Not homogenous

Merit: Greater representation of each strata of sample.

Method: Population under study

Division into homogenous groups

Sampling drawn from each stratum at random in proportion to its size.

Example:in order to determine prevalence of hemoglobinopathies in India, the equal number of children from Hindus, Sikhs, Christians and Muslims need to be selected.

The commonly used Probability sampling techniques are:

  1. Simple random sampling
  2. Systematic sampling
  3. Stratified sampling
  4. Multistage sampling
  5. Cluster sampling

Different sampling techniques are used according to their appropriateness in the study and the population.

Sample: Essential characteristics

Adequate size (30 or more)

Random selection

a. Simple random sampling

Every unit of population has an equal chance of being selected

It is applicable when the population is: Small, Homogenous, and readily available

Examples:

Patients coming to hospital

Ward patients

b. Systematic sampling

It involves choosing elements in a systematic way – such as every fifth patient admitted to a hospital or every third infant born in an area after having selected the first number randomly. This type of sampling provides the equivalent of a simple random sample without actually using randomization.

It is used when the population is:

Large

Scattered

Not homogenous

Popularly used in those cases when a complete list of population, from which sample is to be drawn, is available.

Biostatistics Flashcard List

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