Confidence Intervals (Mean)

Question

If n = 10, ¯xx¯ = 47, and s = 7, construct a confidence interval at a 80% confidence level. Assume the data came from a normally distributed population. Give your answers to three decimal places. 

Answer 1

X bar = 47 +- t_{crit X 7 / sqrt 10}

X bar = 47 +- 1.383 X 7/3.162

Xbar = 4.7 +- 1.383 X 2.214

X bar = 4.7 +- 3.061

LCL = 1.639

UCL = 7.761