What is the appropriate method to calculate sample size for retrospective drug utilization studies?
For example, i want to look how many drugs on an average (and which drug categories), were being consumed by patients by checking the specific diabetic medical records.
Does the formula..... sqr(1.96) x sqr(SD) / sqr (d) works here.
Thanks in advance!
Go to this site:
https://www.surveymonkey.com/mp/sample-size-calculator/
It largely depends on your planned analyses not just on the variance and targeted margin of error. For instance, if you want to segment your respondents you need larger sample size. Observational data (your study is in that category, you won't manage the dosage and the control) need larger sample to represent the different cases. I would assume you need minimum 100 and above 300 you are good, it depends on your segmentation (clustering) needs.
Do you have linear correlation of cost and sample size? What are your constraints? Usually I just collect as many responses as I can except I do have a constraint.
You can benefit from the following links.
1. S R Jones, S Carley, M Harrison. An introduction to power and sample size estimation. 3 Emerg Med J2003 20: 453-458
2. Sathian B, Sreedharan J, Mittal A. Importance of Sample Size Calculation in the Original Medical Research Articles
3. Bachhav SS, Kshirsagar NA. Systematic review of drug utilization studies & the use of the drug classification system in the WHO-SEARO Region. The Indian Journal of Medical Research. 2015;142(2):120-129. doi:10.4103/0971-5916.164223.
4. Sagar BachhavNilima A. Kshirsagar. Systematic review of drug utilization studies & the use of the drug classification system in the WHO-SEARO Region. The Indian Journal of Medical Research 142(2):120-12.
5. Birhanu Demeke, Fantahun Molla ,Admassu Assen, Wondim Melkam, Solomon Abrha , Birhanetensay Masresha , Tigist Asef .EVALUATION OF DRUGS UTILIZATION PATTERN USING WHO PRESCRIBING INDICATORS IN AYDER REFERRAL HOSPITAL, NORTHERN ETHIOPIA. International Journal of Pharma Sciences and Research (IJPSR) .6 (2); Feb 2015;343-347.
Check this link . I hope will help you
http://apps.who.int/medicinedocs/en/d/Js2289e/4.4.html
regards
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