Power is the probability that a study will reject the null hypothesis. difference between the null and alternative hypotheses. level of significance, and the null vs. alternative difference. a numeric example of power and sample size estimation for the one-sample case.
During the procedure the patient is unconscious and unaware of the need to urinate. After the procedure, however, it may not be safe for the patient to walk. They may be too sick to take care of their own bathroom needs or their surgeon may feel that a catheter is best for their particular recovery.
Most catheters are necessary until the patient regains the ability to urinate on their own, which is usually a short period of time. Elderly people and those with a permanent injury or severe illness may need to use urinary catheters for a much longer amount of time and sometimes on a permanent basis.