The population sample must be truly representative of the population to be studied. The method used to collect the sample must be convenient for the sampler. The sample can be collected randomly or following a quota for each group.
The sample size depends on the population size and the accuracy needed from the study.
Questionnaires were not used because key personal determining the factors affecting price changes in gasoline were not accessible. Other data was collected by use of interview with gas station personnel to gather their opinion concerning possible causes for changes in gasoline prices.
Good research provides new and unbiased findings that are important to some entity or group of people. The researcher must not benefit from the outcomes and findings of the study as to ensure the integrity of the findings. Information collected should best represent the population that is being tested. Good research utilizes the most appropriate data collection methods such as surveys, interviews, etc and research tools such as periodical indexes, databases, and Web sites.
If the null hypothesis is not rejected, then the alternate hypothesis is not accepted. This is because the initial sample of 30 records did not provide enough information to infer statistically significance of the hypothesis to be tested.