I conducted a controlled experiment to test the effect of a training intervention on workers. We were allocated 40 workers at the start by an NGO. This allocation was random as the workers were selected randomly from the pool of workers that the NGO knew. After this, we randomly divided the workers equally into two groups - treatment and control (20 and 20) and kept all other variables and conditions same for both, e.g. the regular activities of the workers. We then provided a month-long training on a topic to the workers in the treatment group. To know whether the training had some effect on the knowledge of the workers in the treatment group, we tested the knowledge of both the groups before and after the intervention. We found the two groups to differ in their knowledge at the baseline; the average percentage of the pre-test scores for the treatment group was 34%, and the control group was 28%. The difference was statistically significant (Wilcoxon sum test, p < 0.05). We use the Wilxocon tests as the data was not parametric. I would like to know what could be the potential factors which led to this difference.
Dividing the participants equally into two groups - treatment and control - by random process usually results in comparable baseline characteristics. Before commenting on the statistically significant baseline knowledge difference that you obtained it is better to know the following two things: a). what are the random methods adopted in each stage? i.e., simple or systematic, multistage, etc... b). it is mentioned '....and kept all other variables and conditions same for both, e.g. the regular activities of the workers.' what do you mean by 'all other variables same for both'. The conditions can be kept same for both but not the variables. Is there any additional restrictions on variables.
Hi,
compare pre and post scores by paired t-test in each group separately and comment on the change in each group. Can be converted to percentages.
knowledge is a random variable and people can have some degree of prior knowledge. That may not be matched. Matching can be on sociodemographic, years of service, etc.,
Thanks, Dr. Ravichandran for your response and the correction. By conditions, I meant to say all other activities other than our training intervention. These included routine duties of the workers, their routine interactions with supervisors and peers. The selection of the participants was two-staged. At the first stage, the NGO selected the participants from their pool of total workers. I do not have the full information on exactly what technique they used for the selection. At the second stage, which is dividing the participants into two groups, I used random number generator function for the allocation.
- Badges
- Science topic
- Similar topics
- Organizational Psychology
- Training