Sample:
Representative subset of population is called sample.
Sampling:
The process of data collection from sample is called sampling.Population:
Collection of all the elementary units is called population.Census:
Collection of data from population is called census.Sampling;
Estimates parameter from sample for population.
• Decision making through sample is always a concerned for population.
• Decision making through sample is always a concerned for population.
Estimation;
Generalizing through sample for whole population is estimation.
Why sampling is done?
As it is economic efficient;
2. less costly
3. minimum resources required
4. If population size is larger, then best equality data obtained through sampling rather than census.
1. time saving
As it is economic efficient;
2. less costly
3. minimum resources required
4. If population size is larger, then best equality data obtained through sampling rather than census.
1. time saving
Decision in Sampling:
1. Sampling unit; To when you collects data.
2. Sampling Size; Size of the sample.
3. Sampling Techniques;
1. Sampling unit; To when you collects data.
2. Sampling Size; Size of the sample.
3. Sampling Techniques;
Sampling Techniques:
1. Probability Sampling Techniques:
If their are equal and non-zero chances for every elementary unit of the population to be selected in the sample.• It is a scientific technique.
• In hypothesis or parametric ( mean and standard deviation both can calculated). statistics; it is implied that probably sampling Techniques should be used in selecting sample.
Sample Frame;
• Without sample Frame, probability sampling Techniques is not possible.
• Without sample Frame, probability sampling Techniques is not possible.
The list of all elementary units of population is called sample Frame.
» The probability sampling Techniques are;
A. Sample Random Sampling:
• Randomly selection of representatives from sample without dividing into groups.• Every elementary unit has equal and non-zero chance of selection.
• Sample random sampling is usually done through computer software by using sampling frame.
B. Systematic Random Sampling:
K= N( population size ) /n (Sampling size) = 50 / 5 = 10
• Divide the sample into groups with respective interval of K no.
a. 1–10 b. 11–20 c. 21–30 d. 31–40 e. 41–50
(Randomly selects one no. from group. 1 like 7 now add 10 into it; 7+10 = 17 , 17+10 = 27 , 27+10 = 37 , 37+10 = 47; representative are ( 7, 17, 27, 37, 47) and interval is of 10 in groups).
C. Stratified Random Sampling:
• Stratified words comes from; stratum mean homogenous group, plural of stratum is strate and the process is called stratification.
• Population divided into homogenous group ( common characteristic) based on the characteristic of interest and then select randomly.
• In stratetied Random sampling; within the group is homogeneity and across the group is heterogeneity.
• Sampling should be done from all groups.
• Like if area of interest of grouping is based on gender then 2 groups were formed; male and females, homogeneity lies and heterogeneity lies across the group that other group is if purified male, no any female is in it.
• Population divided into homogenous group ( common characteristic) based on the characteristic of interest and then select randomly.
• In stratetied Random sampling; within the group is homogeneity and across the group is heterogeneity.
• Sampling should be done from all groups.
• Like if area of interest of grouping is based on gender then 2 groups were formed; male and females, homogeneity lies and heterogeneity lies across the group that other group is if purified male, no any female is in it.
Cluster Sampling:
• In cluster sampling; within the group is heterogeneity and across the group is homogeneity.
• Randomly selects some group cluster's from all cluster's and select representative from selected cluster's.
• Cluster sampling is done when group are geographically far from eachother.
It is done because it involves less time, less cost and less resources.
• If sampling is done from country for income level checking groups of provinces were made ; Punjab, Sindh, Balochistan, KPK.
• In this sampling within the group is heterogeneity that high, low, average, different income is homogeneity thath all four group possess different groups of income.
• Randomly selects some group cluster's from all cluster's and select representative from selected cluster's.
• Cluster sampling is done when group are geographically far from eachother.
It is done because it involves less time, less cost and less resources.
• If sampling is done from country for income level checking groups of provinces were made ; Punjab, Sindh, Balochistan, KPK.
• In this sampling within the group is heterogeneity that high, low, average, different income is homogeneity thath all four group possess different groups of income.
Multi-Stage cluster Sampling:
• Divide group to further to further to different levels.
• First four clusters formed, randomly selects two cluster for sampling again further divide into six groups then randomly selects and groups from both two clusters then further divide it.
• First four clusters formed, randomly selects two cluster for sampling again further divide into six groups then randomly selects and groups from both two clusters then further divide it.
2. Non-Probability Sampling Techniques:
• In the absence of sample frame, non probability sampling technique was referred otherwise it was not appreciated because it is less scientific and no proper data was obtained.
a. Convenience Sampling:
• It is not used for all studies in hypothesis and parametric testing, the results obtained from this technique gets null and void.
• It is used for qualitative purpose and idea generating purpose to bring creativity and evidence the product or bring new product.
• Like if you are going to take interview of Manager's of Karachi bank and you select Ten bankes which are nearer to your hometown is convenience sampling not simple random sampling.
• It is used for qualitative purpose and idea generating purpose to bring creativity and evidence the product or bring new product.
• Like if you are going to take interview of Manager's of Karachi bank and you select Ten bankes which are nearer to your hometown is convenience sampling not simple random sampling.
b. Judgement Sampling:
• If a person is deciding on behalf if his/her own personal skills, abilities and experience that who should be selected is a representative in sampling in judgement Sampling.
• Like if IQ level of class was check and teacher selects students from class on personal experience is judgement sampling.
• Like if IQ level of class was check and teacher selects students from class on personal experience is judgement sampling.
c. Snowfall Sampling:
• If respondent for sampling is not easily available by finding one respondent we reach to 2nd respondent by 1st respondent reference, some till all the respondent then it is snowfall sampling.
• Like if sampling is an beggars or a rare psychology disease study and its petients.
• Like if sampling is an beggars or a rare psychology disease study and its petients.
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