Historical records over the past 10 years indicate that 20 percent of the major surgery patients are dissatisfied with after-surgery care in the hospital. An analyst conducted a scientific poll based on 400 hospital patients and found that 64 were dissatisfied with their after-surgery care. Find the standard deviation of the sampling distribution of the sample proportion.

Use Excel or JMP to find probabilities and values. Do not round intermediate calculations. Round your final answer to four decimals. Use number format 0.0000 Do not use probability tables to find probabilities.