Question

研究表明，按摩疗法具有多种健康益处，而且价格也不算太贵。12个典型的一小时按摩疗法疗程的样本显示平均费用为58。一小时疗程的人群标准偏差为5.5。

b。 使用90％的置信度，误差范围是多少（小数点后2位）？

c. Using 99% confidence, what is the margin of error (to 2 decimals)?

Answer 1

Given that, sample size (n) = 12

sample mean (M) = 58

sample standard deviation (s) = 5.5

=> Degrees of freedom = 12 - 1 = 11

a) t-critical value at significance level of 0.10 with 11 degrees of freedom is,

We want to find the margin of error (E),

=> Margin of error = E = 2.85

b) t-critical value at significance level of 0.01 with 11 degrees of freedom is,

We want to find the margin of error (E),

=> Margin of error = E = 4.93