D CHART: demerit chart

DECISION MATRIX: a matrix used by teams to evaluate problems or possible solutions. After a matrix is drawn to evaluate possible solutions, for example, the team lists them in the far-left vertical column. Next, the team selects criteria to rate the possible solutions, writing them across the top row. Third, each possible solution is rated on a scale of I to 5 for each criterion and the rating recorded in the corresponding grid. Finally, the coatings of all the criteria for each possible solution are added to determine its total score. The total score is then added to help decide which solution deserves the most attention.

DEFECT: a product's or service's non-fulfillment of an intended requirement or reasonable expectation for use, including safety considerations. There are four classes of defects: Class 1, Very Serious, leads directly to severe injury or catastrophic economic loss; Class 2, Serious, leads directly to significant injury or significant economic loss; Class 3, Major, is related to major problems with respect to intended normal or reasonably foreseeable use; and Class 4, Minor, is related to minor problems with respect to intended normal or reasonably foreseeable use. (See also "blemish, "imperfection" and "nonconformity.")

DEGREES OF FREEDOM: a parameter in the t, F, and x2 distributions. It is a measure of the amount of information available for estimating the population variance; s2. It is the number of independent observations minus the number of parameters estimated.

DEMERIT CHART: a control chart for evaluating a process in terms of a demerit (or quality score), i.e., a weighted sum of counts of various classified non-conforinities

DESIGN OF EXPERIMENTS (DOE): a branch of applied statistics dealing with planning, conducting, analyzing, and interpreting controlled tests to evaluate the factors that control the value of a parameter or group of parameters:

DISTRIBUTIONS: see “Probability Distribution”.

EXPERIMENTAL DESIGN: a formal plan that details the specifics for conducting an experiment, such as which responses, factors, levels, blocks, treatments, and tools are to be used

EXPONENTIAL DISTRIBUTION: a probability distribution mathematically described by an exponential function. Used to describe the probability that a product survives a length of time t in service under the assumption that the probability of a product failing in any small time interval is independent of time.

FACTOR: an assignable cause which may affect the responses (test results) and of which different versions (levels) are included in the experiment.

FACTORIAL EXPERIMENTS: experiments in which all possible treatment combinations formed from two or more factors, each being studied at two or more versions (levels), are examined so that interactions (differential effects) as well as main effects can be estimated.

F DISTRIBUTION: distribution of F-statistics.

F STATISTIC: a test statistic used to compare the variance from two normal populations.