Data Reduction (Factor Analysis, Principal Components Analysis)
Interviews often include a large battery of attitudinal or product ratings statements. These techniques aim to reduce the number of variables into a few underlying structures, called factors. This is done to make interpretation easier, since the researcher only needs to consider the factors, and also allows more robust analysis since the factors are statistically independent.

Database
A centrally-held collection of information which enables access and alteration by one or many users.

Database Management
The monitoring, upkeep and operation of the database, ensuring all information is up-to-date and relevant.

Database Marketing
A form of marketing where messages are sent to specific target groups as a result of detailed information about their characteristics.

Decision Analysis (Clinical)
A systematic approach to analyzing the certain and uncertain decision-making options and consequences to health in relation to the diagnosis and treatment of diseases under different circumstances. (It is illustrated through a decision-tree).

Decision Tree
A pictorial representation of decision analytic options, pathways and outcomes.

Defined Daily Dose (DDD)
The assumed average maintenance dose per day for a drug used in its main indication in adults.

Delphi Method
A research method used to gain a consensus view from a group of individuals.

Demographic Segmentation (see Segmentation)

Dependent Variable / Dependence (see Variable)

Depth Interview (see Research Interviews)

Descriptive Research (see Research Studies)

Detail Aid
A brochure or pamphlet summarizing key selling points related to a product or service. Used by sales representatives in conversation with customers, usually in a one-to-one situation.

Diary (in Market Research) (see Research Studies)

Dichotomous Question (see Research Questions)

Direct Costs
All costs that arise from direct health consequences.

Direct Mail
A piece of promotional literature which is mailed to selected target audiences.

Direct Marketing
Supplying a product or service direct to the consumer without using a retail outlet.

Direct Medical Costs
All costs that are due to the materials, personnel time and capital consumed as a result of a healthcare intervention.

Direct Question (see Research Questions)

Discount Rate
A numerical factor for converting future costs and benefits into present values for the purpose of economic evaluation.

Discrete Choice Methods (DCM)
A group of techniques to determine the choices made by respondents and the trade-offs between different product offerings. Closely related to Conjoint Analysis - seen by some as an alternative to it, and by others as a type of conjoint methodology. Questioning is based on choice of product, rather than preference between products. Also known as Choice-Based Conjoint (CBC).

Discriminant Analysis
A specific type of criterion-based cluster analysis, which aims to predict group membership, based on a series of variables.

Discussion Guide (see Research Questions)

Disease Management
The process of considering all aspects of treating or managing a disease, not just the therapeutic management element. This term has in some cases been replaced by the term 'health outcomes management'. Disease Management is used in managed care to refer to a comprehensive approach to the delivery of preventative and curative care of illnesses based on sound evidence of effectiveness with a view to improving quality at reduced costs.

Display Advertising
Advertising other than simple typeset adverts.

Disproportionate Stratified Random Sampling (see Sampling Methods)

Distribution (of Drug)
The transfer of drugs after absorption from the blood stream to different organs and tissues of the body.

Dog
Product or service which is retained in a company's portfolio, but is not generating sufficient income to cover its costs. i.e. low market share and low market growth. Product retention may be for sentimental reasons. (see also Product Positioning)

Domain (see Health Status Instrument)

Dosage Regimen
The recommended quantity of a drug to be ingested per interval of time.

Dose Range Finding (Dosimetry)
Determination of the appropriate quantity of a drug to be administered based on factors such as its pharmacological properties and subjects' age, sex, body mass and surface area.

Double Blind
A feature of clinical trial design in which neither the investigator nor the subjects know which patients are receiving the test drug and which are receiving the 'control' (or placebo) substance.

Double Dummy
A procedure whereby placebo tablets are substituted for active substance to maintain constant number of test formulations.

Drug and Therapeutics Committee (DTC)
Expert group from within hospital or provider which decides what pharmaceuticals are approved for the formulary.

Drug Development
The processes involved in the discovery, pre-clinical testing, clinical evaluation, formulation and approval of a new drug until it reaches the market.

Drug Elimination
The processes whereby intact drugs or their metabolic products are cleared from the blood circulation by organs such as the kidney or liver.

Drug Interactions
The unexpected effects of combining 2 or more drug substances (e.g. potential activity, reduced bioavailability, adverse reactions).

Drug Usage/Utilization Review (DUR)
A process involving the review, analysis and interpretation of the costs and appropriateness of use of drugs. Also referred to as Drug Use Evaluation (DUE).

DTC Advertising
Direct To Consumer advertising of prescription medication, in countries where permitted, usually comprises advertisements in newspapers and magazines, and point-of-sale promotions.

Dyadic
A product test in which people are asked to compare two products. Also known as a Paired Comparison. (see also Monadic Test and Triadic Test)