Use the Microsoft Excel function CONFIDENCE.NORM to find the confidence interval for a population mean of $19 at a 95% level of confidence with a sample size of 12 and standard deviation of $1.8.
A)$17.98 to $20.02
B)$18.97 to $19.03
C)-$4.52 to $42.52
D)$17.20 to $20.80

Question

Quizplus · Accepted Answer

Using the formula:
Confidence Interval = sample mean ± CONFIDENCE.NORM(alpha, standard_deviation, sample_size) * standard_error

where:
alpha = 1 - confidence level (in decimal form)
standard_error = standard_deviation / sqrt(sample_size)

Plugging in the values:
alpha = 1 - 0.95 = 0.05
standard_error = 1.8 / sqrt(12) = 0.52

CONFIDENCE.NORM(0.05, 1.8, 12) = 1.96

sample mean = 19

Confidence Interval = 19 ± 1.96 * 0.52 = $17.98 to $20.02

Therefore, the best choice is A.

Use the Microsoft Excel Function CONFIDENCE