Answer:
a: 258.09
b: 178.88
Step-by-step explanation:
For a: Since n > 30, we use a z-value that corresponds to 0.01, or 99% confidence. This z-value is: 2.575
We have:
x = 265, n = 459, σ = 50. See the calculation for the error and the construction of the confidence interval on the first attached photo
For b: Since n > 30, we use a z-value that corresponds to 0.05, or 95% confidence. This z-value is: 1.96
x = 180, n = 308, σ = 10 (it gives σ² = 100. so σ = 10). See the calculation for the error and the construction of the confidence interval on the second attached photo