Final answer:
To estimate the mean time that a staff member spends with each patient, use the formula N = (Z * σ / E)^2, where N is the sample size, Z is the Z-value for the desired confidence level, σ is the population standard deviation, and E is the desired margin of error. Applying the formula, a sample size of 241 is needed.
Step-by-step explanation:
To estimate the mean time that a staff member spends with each patient, we need to determine the sample size required to achieve a desired margin of error at a 95% level of confidence. We can use the formula:
N = (Z * σ / E)^2
Where:
N = required sample size
Z = Z-value for the desired level of confidence (in this case, 1.96 for 95% confidence)
σ = population standard deviation (given as 12 minutes)
E = desired margin of error (given as 3 minutes)
Substituting the given values into the formula, we have:
N = (1.96 * 12 / 3)^2
N = 15.52^2
N ≈ 240.8
Rounding up to the nearest integer, the required sample size is 241.