Question

1. In a random sample of 12 two-month-old baby girls, the sample mean weight was 11.40 pounds and the population standard deviation was 1.80 pounds. Assume that the population of weights for two-month old baby girls is approximately normal.

a) Construct a 98% confidence interval for the population mean weight of two-month-old baby girls. Be sure to include the following:

1. The formula that’s used to calculate the confidence interval.

2. If you used a built-in calculator program to compute the lower and upper bounds, then

   write out which program you used and the numbers that you entered into your calculator,

   along with their corresponding variables.

3. If you didn’t a built-in calculator program, then write out the expression you entered into

   your calculator to compute the lower and upper bounds.

b) Interpret your confidence interval from (a). Include the following in your interpretation:

1. The confidence level.

2. The population parameter of interest (in the context of the problem).

3. The lower and upper bounds, along with the correct units.

- Find the area under the standard normal curve to the left of z = -0.94. Draw a sketch to illustrate the desired area and write out what you entered into your calculator to compute your answer.

Answer 1