## Noncentral distributions :

A noncentral distribution is a statistical distribution that is not centered around its mean value. This means that the distribution has a nonzero mean value, but the values of the distribution are not evenly distributed around that mean value. Instead, the values may be skewed or asymmetrical, with a higher concentration of values on one side of the mean value. There are two main types of noncentral distributions: noncentral t-distributions and noncentral chi-squared distributions.

One example of a noncentral distribution is the noncentral t-distribution. The t-distribution is a distribution that is used to analyze data sets with small sample sizes, and it is often used in statistical hypothesis testing. The noncentral t-distribution is used when the mean value of the distribution is not equal to zero, and it can be used to analyze data sets with small sample sizes that are not normally distributed.

For example, suppose that a researcher is studying the average height of men in a certain population. The researcher collects a sample of 50 men and measures their heights, and finds that the mean height is 5’10”. However, the researcher knows that the population mean height is actually 6’0″, and the sample size is too small to accurately represent the population. In this case, the researcher could use the noncentral t-distribution to calculate the probability that the mean height of the sample is significantly different from the population mean height.

Another example of a noncentral distribution is the noncentral chi-squared distribution. The chi-squared distribution is a statistical distribution that is often used to test the goodness of fit of a model to a set of data. The noncentral chi-squared distribution is used when the mean value of the distribution is not equal to zero, and it can be used to test the goodness of fit of a model to a set of data that is not normally distributed.

For example, suppose that a researcher is studying the behavior of a certain type of animal in a particular environment. The researcher collects a sample of 100 animals and observes their behavior, and finds that the mean behavior of the sample is significantly different from the expected behavior of the population. In this case, the researcher could use the noncentral chi-squared distribution to calculate the probability that the mean behavior of the sample is significantly different from the expected behavior of the population.

Overall, noncentral distributions are useful for analyzing data sets that are not normally distributed, and for testing the goodness of fit of a model to a set of data. They allow researchers to accurately assess the probability that the mean value of a sample is significantly different from the expected mean value of a population, and to identify patterns or trends in data sets that may not be apparent using other statistical methods.