Instructions to conduct a work sampling study in groups

Important: When conducting a work sampling study, the researcher and the stakeholders share the mission of the study with the people being studied.

A. Decide on a mission of the project - the objective of the study is being detailed in this stage. This can be done by answering a set of questions, like: Why is the study performed? What are the results the researcher is after? Is the target activity a grouped one (like indirect work) or a detailed activity (like waiting time)? Will the study be performed through outside consultantsinside people or self-reported? The list of questions differs from one study to another. The main idea is to capture the scope of the project, detailing the expectations and needs.

Even if this step can be easily overlooked or minimized, it is critical to conduct a thorough analysis about the mission of the project at this point. Not doing this can cause issues on data reliability and validity that can only be corrected with losses both on financial and personnel levels.

The baseline parameters that are chosen include;

B. Again if you are working manually or with old technology you must do some calculations and make some decisions:

The calculation of the total number of observations needed to obtain the desired accuracy. As a consequence, the number of observations can be adjusted to meet certain levels of precision that are considered acceptable by the researcher.

For an automated nomograph to calculate the number of observations go to Choose the right number of observations (Nomograph)
The formula used to calculate the total number of observation is explained in more depth on the Mathematics tab.

n = (t2 * p(1-p))/m2
Where;
n = number of observations needed
t = confidence level (standard value) - the confidence level consists of the probability that the results obtained are included in a specified range. Usually researchers use a 95% probability for which t=1.96.
m = margin of error - for example +/-2% accepted variation from final results.
p = estimated prevalence of targeted activity declared at the beginning of the project.

For group level studies, after the total number of observations is calculated, the individual number of observations can be determined using the following formula:
nindividual = n/number of individuals

The scheduling of randomly chosen time points for observations. At this stage, the researcher has available inputs about: start date of study, total/individual number of observations, and structure of working schedule (working hours and working days taken into consideration). If the end date of the study is already established, the mean time between observations can be calculated and used for randomization of observations.

The formula used for calculating mean time between observations (MTBO - expressed in minutes) is:
MTBOtotal = Total number of working minutes from start date until end date/n
MTBOindividual = Total number of working minutes from start date until end date for each individual/nindividual

When randomizing the time points for observations based on the formulas described above, there are specific guidelines that can be considered:

C. To define the list of activities The challenge of defining work categories is to be detailed enough to comprise all the anticipated work activities and to give also the possibility to the individual to detail manually an activity if no category contains it. To reduce the number of manual interventions and to ensure data consistency, the definitions of the work activities and categories must be clear and concise.

D. To design all necessary forms and templates for data collection that will contain details about the study parameters (routes, observation points etc).

E. To select and train individuals that will have responsibilities in the survey. This stage is essential for obtaining accurate and reliable data. The motivation and implication of all members involved is a key attribute of a successful work sampling study.

F. Conduct data collection (Make the observations). Once the above calculations have been completed, the observations begin and activities are recorded at the agreed time intervals. When they have been completed, a reverse calculation can be used to determine the margin of error, as follows:

In this case, n is the actual number of observations registered in field for all individuals or equipments (sum of all nindividual values).

A pilot study can also be undertaken. During this period, the definitions of the work categories are tested and adjusted, if needed. Also, valuable information about a preliminary structure of activities is calculated and used for measuring more efficiently the actual study parameters. It is also important to have a supervisor that continuously monitors that the collection phase is going according to schedule.

G. To analyze results and prepare reports with recommendations. The information obtained from each observation is centralized and used for analysis. If bias is thought to have appeared during the first hours or days of the survey, it is recommended to exclude the suspicious data from the analysis. In this case, the remaining observations are assessed for accuracy and reliability based on the formulas presented in the previous sections.

Work sampling provides baseline information for change and improvement. The reports that can be built after the analysis has been finalized relate to: