stat 145

STAT 145 ONLINE Week Ten Assignment Complete the week 10 assignment by entering your answers onto the accompanying answer sheet (either typed or handwritten). Upload the completed answer sheet to the appropriate dropbox in myCourses by the due date provided on the course calendar. This can be completed as an individual or team assignment. A team recording does NOT need to be completed.

Carol Marchetti and Birgit Coffey

School of Mathematical Sciences, Rochester Institute of Technology.

Problem #1 – Sample Size

A researcher wants to estimate the mean hours per week that Americans spend watching television. He has read an article about a survey conducted in 2014 that had s = 7.5 hours per week spent watching television. What sample size does he need to estimate the population mean within 2 hours per week with 95% confidence? SHOW YOUR WORK.

Problem #2 – Bacteria The pasteurization process reduces the number of bacteria found in dairy products, such as milk. The following data represent the counts of bacteria in pasteurized milk (in CFU/mL) for a random sample of 12 pasteurized glasses of milk. Data courtesy of Dr. Michael Lee, Professor, Joliet Junior College.

a. Construct a 95% confidence interval for the population bacteria count found in pasteurized milk.

To do this, please show the steps (Population, Method, Sample, Results, Conclusion). b. Suppose a student miscalculated the number of bacteria and recorded a result of 2.3 x

105. We would include this value in the data set as 23.0. What effect would this additional observation have on the 95% confidence interval? (You do not have to build a new interval; just write about the effect this additional data point would have.)

NOTE: Each observation is in tens of

thousands. So, 9.06 represents 9.06 x 104.

Week 10 Assignment 2

Problem #3 The concentration of mercury in lake waters is important to monitor (too much mercury can cause serious health problems). A recent accident at a lakeside factory may have leaked mercury into the water. So a team of environmentalists collected containers of water from randomly selected locations in the lake and measured the mercury concentration (mg/m3) in each. See the sample below:

1.60 1.45 1.77 1.52 1.61 1.43 1.25 1.98 0.98 1.20 1.79 0.85 1.34 2.11 1.07

Estimate the mean mercury level in the lake with 90% confidence.

A. Work through the STEPS (Population, Method, Sample, Results Conclusion) to estimate the population characteristic.

FOLLOW UP QUESTIONS:

B. Is a mean mercury level of 1.25 mg/m3 reasonable based on your CI? Explain your decision.

C. Is a mean mercury level of 1.60 mg/m3 reasonable based on your CI? Explain your

decision.

D. A statement was made that the mean mercury level in the lake is more than 1.25 mg/m3. Does the CI support this statement? Explain.

E. A statement was made that the mean mercury level in the lake is less than 1.50 mg/m3. Does the CI support this statement? Explain.