Question

A sample of 18 small bags of the same brand of candies was selected. Assume that the population distribution of bag weights is normal. The weight of each bag was then recorded. The mean weight was 3 ounces with a standard deviation of 0.12 ounces. The population standard deviation is known to be 0.1 ounce.

NOTE: If you are using a Student's t-distribution, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.)

Construct a 98% confidence interval for the population mean weight of the candies.

(i) State the confidence interval. (Round your answers to three decimal places.)

(ii) Sketch the graph.

(iii) Calculate the error bound. (Round your answer to three decimal places.)

Answer 1

i) At 98% confidence level, the critical value is z_0.01 = 2.33

The 98% confidence interval is

ii)

iii) Margin of error is