Question

1) Karen wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 41 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 19.2 and a standard deviation of 2.7. What is the 80% confidence interval for the number of chocolate chips per cookie for Big Chip cookies? Enter your answers accurate to one decimal place (because the sample statistics are reported accurate to one decimal place).

2)The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 39.2 for a sample of size 445 and standard deviation 9.6.
Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 99% confidence level).
Enter your answer accurate to one decimal place (because the sample statistics are reported accurate to one decimal place).

Answer 1

Using Minitab:

One sample t test steps:

Click Stat > Basic Statistics > 1-Sample t... on the top menu, as shown below:

You will be presented with the following 1-Sample t (Test and Confidence Interval) dialogue box:

Click the OK button. The output that Minitab produces is shown below.

80% confidence interval for the number of chocolate chips per cookie for Big Chip cookies is 18.651, 19.749.

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