A random sample of magnesium concentrations (in parts per million, or ppm) in ground water from various locations follows. Estimate the mean concentration of magnesium in ppm with 90% confidence. Assume .

Question

A random sample of magnesium concentrations (in parts per million, or ppm) in ground water from various locations follows. Estimate the mean concentration of magnesium in ppm with 90% confidence. Assume  .

Quizplus · Accepted Answer

Using a t-distribution and a 90% confidence level with a sample size of 25 (n-1= 24 degrees of freedom), the t-value is 1.711. 
The mean concentration of magnesium is estimated to be:
x̄ ± t*(s/√n)
= 52.4 ± 1.711*(14.27/√25)
= 52.4 ± 5.81
= (46.59, 58.21)
Therefore, the best choice is option B, which is closest to the midpoint of the confidence interval, 52.4.

A Random Sample of Magnesium Concentrations (In Parts Per Million