Changes in one variable depend on changes in another variable. Measures of central tendency are summary statistics or descriptive statistics used to indicate the central location of a group of data values. The three most commonly used measures of central tendency are the mean , the median , and the mode . Chi-square tests are frequently used to detect significant relationships between two variables measured on nominal scales, or to determine whether a distribution differs significantly from expectations. Chi-square tests belong to the class of statistical inferential procedures known as nonparametric or distribution free tests.
Correlation refers to the degree of relationship among variables .
A correlation coefficient is a measure of the degree of relationship among variables. There are many correlation coefficients. The Pearson is parametric and the Spearman is a nonparametric measure of relationship. More generally dependent variables values depend upon the values of independent variables. A distribution or, more formally, a frequency distribution is simply a table, chart or graph which pairs each different value obtained from a sample or population with the number or proportion of times it occurs.