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.
When the catheter is in the bladder, a small balloon is inflated to keep the catheter in place. The urine drains from the bladder into a bag that is usually attached to the thigh. Sometimes the catheter tube has a valve that lets you drain the urine into the toilet or other container. You may need this type of catheter if you have nerve damage or if you have problems with your bladder or urethra.