Confidence interval calculator
Confidence interval is the plus-or-minus figure which is one of the indications of how your findings are the same as the opinions of the whole population. For example, you have a confidence interval of 4 and 32% percent of your respondents answered "no" to the question if they would buy your product again. In that case you can be "sure" that if you had asked the question to the entire relevant population between 28% (32-4) and 36% (32+4) would have picked that answer. The following tool can be used to calculate what confidence interval your research project has. An explanation of the used terms can be found by clicking on them.
Confidence level
In statistics, a confidence interval is a particular kind of interval estimate of a population parameter. Instead of estimating the parameter by a single value, an interval likely to include the parameter is given. Thus, confidence intervals are used to indicate the reliability of an estimate. How likely the interval is to contain the parameter is determined by the confidence level or confidence coefficient. Increasing the desired confidence level will widen the confidence interval.
A confidence interval is always qualified by a particular confidence level, usually expressed as a percentage; thus one speaks of a "95% confidence interval". For a given estimation procedure in a given situation, the higher the confidence level, the wider the confidence interval will be.
In market research, often a confidence level of 5% is used.
Source: Wikipedia
Sample size
The sample of a market research project is the number of observations or respondents taking part in the project. This is not the same as your population. The population stands for the complete target group for your market research project. The sample is mostly a smaller part of the population. Say you want to perform a client satisfactory research. The company you are working for has 4000 clients. Those 4000 clients form the population. If 300 clients take part in the research project, those 300 form the sample. Typically, a larger sample size leads to increased precision in estimates of various properties of the population.
Population
The population stands for the target group for your market research project. This is not the same as your sample. The sample of a market research project is the number of observations or respondents taking part in the project. The sample is mostly a smaller part of the population. Say you want to perform a client satisfactory research. The company you are working for has 4000 clients. Those 4000 clients form the population. If 300 clients take part in the research project, those 300 form the sample. Typically, a larger sample size leads to increased precision in estimates of various properties of the population.
Response distribution
The response distribution is the expected distribution for a question. Normally, if you have a lot of questions or the distribution is hard to forsee, use 50%. This percentage gives the largest sample size, so is the safest choice.
