STUDY POPULATION SAMPLE/INCLUSION AND EXCLUSION CRITERIA Presenters Anne Obondo/Dennis Donovan

Objectives We expect that at the end of this presentation, you will be able to: Define your population sample State your inclusion and exclusion criteria.

Population Generally: Population denotes the number of people within a given boundary www.stats.gla.ac.uk.

In research, Target population Refers the entire group of subjects or participants you wish to generalize the study findings For example, All institutionalized alcoholics Or all university students Or Slum dwellers who abuse alcohol

Accessible population Is the subset of the target population and is also known as the study population. May be limited to region, state, city, county, or institution For example, All institutionalized alcoholics in Nairobi county Or all university students in Nairobi county

Sample and sample frame Is a subset of the population and a typical representative of the larger group or population. Sample frame Is a list of all the participants in the population from which the sample is drawn www.stats.gla.ac.uk

For example, For example, if you study is “assessment of the effectiveness of counseling services in Nairobi” You need a list of all counselling clinics from which you will draw your study sample In opinion polls – electoral register and telephone directory. Gives the participants equal opportunity of being selected as subjects or participants

Effective sample frame Has information about participants. Is organized in a logical and systematic fashion Include every participant of the population No elements from outside the population of interest are present The data is 'up-to-date‘ ( Tunner A. G.,2012)

Illustrative Diagram – Population sample

Relationship between population and sample Population is the entire group Sample is a subset of the population. Before sampling it is important to carefully and correctly define the population Sample is used to make generalizations about a population

Sample must be good size to warrant statistical analysis The more diverse the population the larger the sample. Sample is drawn from the population and the population takes conclusions from the results obtained from the sample.

Research triad

Why sample your population Makes study population easily accessible since it is impossible to study the whole population. Generalization of the findings to the target population can be adequately made. Makes it easy for statistical data analysis However, in qualitative studies you may not need to sample your population

Examples Psychiatric morbidity among adult HIV/AIDS patients attending a comprehensive care centre at a city council clinic in Nairobi. Target population Study population

Problems in study population sample Bias in Selection Sources of bias Omitting people in hard to reach groups Replacing selected individuals with others, because they are in accessible Use of outdated list as sample frame

When population sample is not characteristic of the population. Some members of the population are not included in the frame The non-members of the population are included in the frame. (Leslie Kish, 1995). Being too ambitious

Some points to consider Consider whether your study is quantitative or qualitative. Define your population from which the sample is to be drawn. Consider sample frame with a appropriate contact information Will the population that you want to study meet your objectives

Is my study population accessible? Is my study population representative of the target population? Is it diverse that I can make inferences.

Inclusion and Exclusion Criteria Inclusion criteria are characteristics that the prospective subjects must have if they are to be included in the study. Exclusion criteria are those characteristics that disqualify prospective subjects from inclusion in the study. http://learn.yale.edu/hsp/module_5/3a_guidance.asp

Inclusion and exclusion criteria may include factors such as age, gender, race, ethnicity, type and stage of disease, the subject’s previous treatment history, and the presence or absence (as in the case of the “healthy” or “control” subject) of other medical, psychosocial, or emotional conditions. Defining inclusion and exclusion criteria increases the likelihood of producing reliable and reproducible results, minimizes the likelihood of harm to the subjects, and guards against exploitation of vulnerable persons http://learn.yale.edu/hsp/module_5/3a_guidance.asp

General Population of Interest Inclusion Criteria Exclusion Criteria Sample

SMART-ED Inclusion Criteria 18 years old or older Seeking medical treatment at the ED Had adequate English language proficiency Were capable of providing informed consent Had a score of 3 or greater on the 10-item Drug Abuse Screening Test (DAST-10) Reported at least 1 day of drug use in the 30 days prior to screening Were willing to participate in the protocol Had access to a telephone.

SMART-ED Exclusion Criteria Prisoners or in police custody Currently engaged in or actively seeking addiction treatment Resided more than 50 miles from the follow-up location Were unable to provide sufficient contact information Had already participated in the study.

Screening and Randomization 4,005 participants endorsed past-30d drug use (27% of TADs). Of these, 1,285 were randomized (32% of drug users). Probably most of those not randomized were excluded because they did not meet DAST ≥ 3 criterion.

Pre-Screened: 20762 Screened: 15224 Randomized: 1285 (427 BIB, 427 SAR, 431 MSO) 3-mo f/u: 1026 6-mo f/u: 1107 12-mo f/u: 1043 1 analysis: 1139

References Turner, Anthony G. "Sampling frames and master samples“. United Nations Secretariat, 12/11/2012.  Leslie Kish (1995). Survey sampling. Wiley. ISBN 978-0-471-10949-5. Retrieved 11 January 2011. [