1.)A researcher is interested in finding a 95% confidence interval for the mean number of times per day that college students text. The study included 109 students who averaged 33.8 texts per day. The standard deviation was 14.6 texts. Round answers to 3 decimal places where possible.

1. To compute the confidence interval use a ? z or t distribution.
2. With95% confidence the population mean number of texts per day is between _______ and ______ texts.
3. If many groups of 109 randomly selected members are studied, then a different confidence interval would be produced from each group. About _________ percent of these confidence intervals will contain the true population number of texts per day and about percent will not contain the true population mean number of texts per day.

2.) You are interested in finding a 90% confidence interval for the average number of days of class that college students miss each year. The data below show the number of missed days for 11 randomly selected college students. Round answers to 3 decimal places where possible.

3

6

2

7

8

3

1

12

10

8

11

1. To compute the confidence interval use a ? z or t distribution.
2. With90% confidence the population mean number of days of class that college students miss is between ______ and ______ days.
3. If many groups of 11 randomly selected non-residential college students are surveyed, then a different confidence interval would be produced from each group. About ______ percent of these confidence intervals will contain the true population mean number of missed class days and about ___________ percent will not contain the true population mean number of missed class days.

3.) If n=21, xx(x-bar)=37, and s=6, find the margin of error at a 98% confidence level Give your answer to two decimal places. ____________

4.) If n=41n=41, xx=31, and s=2s=2, construct a confidence interval at a 98% confidence level. Give your answers to one decimal place.

___________< < __________

5.) Karen wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 61 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 5.1 and a standard deviation of 3.1. What is the 95% 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). _______________ < < ______________

6.) You work for the U.S. Food and Drug Administration. You have gotten word that a drug manufacturing is not accurately reporting the contents of their liquid cold medication. Under Federal Regulations, "Variations from stated quantity of contents shall not be unreasonably large" (see section q of the regulation by clicking here). The company that produces the cold medication is claiming that each bottle contains 355 milliliters of cold medication, which is about 12 fluid ounces. In order to determine if they are accurate in their reporting, you decide to randomly select 20 different bottles of cold medication and measure the amount of cold medication in each bottle (in milliliters). The results of each sample are shown below.

Bottle Number	1	2	3	4	5	6	7	8	9	10
Milliliters	356	349	343	356	352	348	358	353	357	346

Bottle Number	11	12	13	14	15	16	17	18	19	20
Milliliters	345	358	346	359	355	348	340	349	350	360

a) Use the data shown above to construct a 94% confidence interval estimate for the mean amount of cold medication the company is putting in their bottles. Record the result below in the form of (#,#). Round your final answer to two decimal places.

_______________________

b) Is the company putting the claimed 355 milliliters of cold medication in their bottles? Explain.

• Yes, because 355 is inside of the confidence interval.
• Yes, because 355 is not inside the confidence interval.
• No, because 355 is inside the confidence interval.
• No, because 355 is not inside the confidence interval.