The main purpose of sampling is to provide qualitative or quantitative information of nature about a scenario by only examining few selected units from the whole. The sample represents the whole nature and the results from the sample give the results of the whole nature. Sampling allows the researcher to avoid wasting time in examining everything in the study area. The sampling method is a scientific procedure that selects units which provides the required estimates to determine the nature of the whole by examining part.
The fundaments of sampling are: Population; Is the collection of all the things that are of interest to the researcher. The population can be either objects or people whom the researcher is interested to do a study. A sample is a representative part of the population. sampling is a technique of getting or identifying a sample from the population. Sampling error is the difference obtained from the values of the sample and the initial value of the population parameter.
Simple random sampling is a probability sampling techniques whereby each unit in the population has the same probability of being in the sample which is used in the study. Random sampling is very efficient when dealing with a low number of objects in the study.
Bias is a systematic error that can jeopardize the evaluation of findings. Biasness can lead to distortion that will give wrong findings and recommendations to the stakeholders and to the researcher. It is important to avoid biasness in research to ensure that the information presented from the research is credible. Surrogate information error is harmful to the researcher and it can be eliminated through conducting an exploratory study and ask the respondents open ended questions to get the required information. The respondents need to have an equal chance to participate in the research. Any sampling that locks out some respondents will lead to biasness and jeopardize information collected. The researcher should also ensure that the population is well represented in the study to avoid one part of the population getting high number of respondents.
Measurement scales are important in research because they provide the researcher with the capacity to know how to group and measure data. The first scale of measurement is the nominal scale, it is the lowest measurement level that includes placing data into different categories without using any order. An example of nominal scale is through using colors or through using yes and no in research.
The second scale of measurement is ordinal scale which is more powerful than nominal. The ordinal scale uses ranking to identify or to group data and through there is no gap left between the two points. The ordinal scale gives the researcher an opportunity to interpret the gross order of the items.
Interval is the standard survey rating scale that is used in researches conducted. The interval scale has equidistance between the units in the study and this gives the researcher an opportunity to interpret distances along a given scale. In this scale of measurement, the researcher is able to give the difference in order and the degree of the order other than ordinal where only a difference is given. Interval scales uses techniques such as mean, median, standard deviation and other statistical techniques.
Ratio is the highest in order as compared to other scales of measurement. Ratio is used in social research to weigh different scenarios. Getting the ratio of different phenomena gives the researcher a hint on the best phenomenon that will bring more advantages than disadvantages.
Reliability is the degree of getting accurate score across the range of measurement. The reliability in the human service research is obtained through inter rater reliability where people are asked the same question and evaluating how they give the answers.
Validity is the extent in which an instrument can give appropriate data in the study. The construct validity is necessary in human service research because it can be able to get the information that is in relation to the theoretical aspect of the study.