Programme: Master of Library & Information Science
Course: MLIS-09: Research Methodology
Target group: Master's students & Research Scholars
Size of the sample means the number of sampling units selected from the population. Size of the sample is directly related to-
- Accuracy
- Time and
- Cost Administration of research study.
The larger the sample, the greater will be the representation of items of the universe. But it is always difficult to manage a large sample.
If the sample size is small, then it may not be representative. Therefore the size of the sample should be kept at the optimum level.
A scientifically selected sample is much superior to a large but badly selected sample.
The size of
the sample depends upon several factors such as –
- Homogeneity or heterogeneity of the population
- Nature of the study
- Type of sampling
- Size of the questionnaire etc.
Size of the sample can be calculated using the following formula:
n=
|
t² x p(1-p)
|
m²
|
Description:
n = required sample size t = confidence level at 95% (standard value of 1.96) p = estimated prevalence of variable in the project area m = margin of error at 5% (standard value of 0.05)Example:
The
appropriate sample size for a population-based survey is determined largely by
three factors: (i) the estimated prevalence of the variable of interest (ii) the desired level of confidence and (iii)
the acceptable margin of error.
Calculate
the sample size for the survey conducted using simple random survey (SRS) taken
from statistics on use of school libraries by high school students in Andhra
Pradesh. Only 30% (0.3) of the schools have libraries. Calculate the sample
size.
n = Calculation:
n = Calculation:
n=
|
1.96² x .3(1-.3)
|
.05²
|
|
n =
|
3.8416 x .21
|
.0025
|
|
n =
|
.8068
|
.0025
|
|
n =
|
322.72 ~ 323
|
Activity:
1. Calculate the sample size for the given parameters using the formula:
n=
t² x p(1-p)
m²
Where t= 95%; p=0.5;
marginal error= 5%
n=
t² x p(1-p)
m²