STAT200 Quiz 3

1 Improving the productivity of chickens. Farmers have discovered that more domestic chickens peck at objects placed in their environment, the healthier and more productive the chickens seem to be. White string has been found to be a particularly attractive pecking stimulus. In one experiment, 72 chickens were exposed to be a sting stimulus. Instead white sting, blue-colored string was used. The number of pecks each chicken took at the blue string over a specified time interval was recorded. Summary statistics for the 72 chickens were x̅=1.13 pecks, s= 2.21 pecks (Applied Animal Behavior Science, Oct. 2008).

Previous research has shown that μ=7.5 pecks if chickens are exposed to white string. Conduct a test (at α=.01) to determine if the true mean number of pecks at blue string is less than μ=7.5 pecks.

 

(a) (8 points)  Formulate the null and  the alternative hypothesis.

(b)(8 points) State and calculate the test statistics from the data.

(c) (8 points) Draw a conclusion.

 

 

2.   A five-year-old census recorded that 20% of the families in a large community lived below the poverty level. To determine if this percentage has changed, a random sample of 400 families is studied and 70 are found to be living below the poverty level. Does this finding indicate that the current percentage of families earning incomes below the poverty level has changed from what it was five years ago? Test with α=0.05.

(a) (8 points)  Formulate the null and  the alternative hypothesis.

(b)(8 points) State and calculate the test statistics from the data.

(c) (8 points) Draw a conclusion.

(d) (8 points) Calculate the P-value.

 

3. A city health department wishes to determine if the mean bacteria count per unit volume of water at a lake beach is within the safety level of 200. A researcher collected 10 water samples of unit volume and found the bacteria counts to be

 

175, 190, 205, 193, 184, 207, 204, 193, 196, 180

 

Do the data strongly indicate that there is no cause for concern?  Test with α=0.05.

 

(a) (8 points)  Formulate the null and  the alternative hypothesis.

(b)(8 points) State and calculate the test statistics from the data.

(c)(8 points) Draw a conclusion.

(d) (8 points) Calculate the P-value.

 

4.  (12 points) A limnologist wishes to estimate the mean phosphate content per unit volume of the lake water. It is known from studies in previous years that the standard deviation has a fairly stable value of σ=4. How many water samples must the limnologist analyze to be 90% certain that the error of estimation does not exceed 0.8 milligrams?

 

 

STAT200 Quiz 3

Attached is document wi...

• Stat 200 quiz.docx 19 KB

STAT200 Quiz 3

1. Decide if the probability described is a subjective (personal) probability or a relative frequency probability: A quarter is flipped 2000 times and results in 500 heads. The 25% (500/2000) chance of heads is a A) subjective probability. B) relative frequency probability. Points Earned: 1.0/1.0 2. A statistics class has 4 teaching assistants (TAs): three female assistants (Lauren, Rona, and Leila) and one male assistant (Josh). Each TA teaches one discussion section. A student picks a discussion section. The two events W = {the TA is a woman} and J = {the TA is Josh} are A) independent events. B) disjoint (mutually exclusive) events. C) each simple events. D) None of the above. Feedback: These events are mutually exclusive since ...

• STAT 200 PSU Quiz 3A+++.docx 72 KB

STAT200 Quiz 3

STAT 200: Introduction to Statistics Final Examination, Spring 2015 OL4/US2 Page 1 of 6 STAT 200 OL4 / US2 Sections Final Exam Spring 2015 This is an open-book exam. You may refer to your text and other course materials as you work on the exam, and you may use a calculator. You must complete the exam individually. Neither collaboration nor consultation with others is allowed. Answer all 25 questions. Make sure your answers are as complete as possible. Show all of your work and reasoning. In particular, when there are calculations involved, you must show how you come up with your answers with critical work and/or necessary tables. Answers that come straight from programs or software packages will not be accepted. If you need to use software (for example, Excel) and /or online or hand-held calculators to aid in your calculation, please cite the sources and explain how you get the results. Record your answers and work on the separate answer sheet provided. This exam has 250 total points. You must include the Honor Pledge on the title page of your submitted final exam. Exams submitted without the Honor Pledge will not be accepted. STAT 200: Introduction to Statistics Final Examination, Spring 2015 OL4/US2 Page 2 of 6 1. True or False. Justify for full credit. (25 pts) (a) If the variance from a data set is zero, then all the observations in this data set must be identical. (b) P(AANDA ) 1, whereA is the complement of A. c c (c) The mean is always equal to the median for a normal distribution. (d) A 99% confidence interval is wider than a 95% confidence interval of the same parameter. (e) It is easier to reject the null hypothesis if we use a smaller significance level α. Refer to the following frequency distribution for Questions 2, 3, 4, and 5. Show all work. Just the answer, without supporting work, will receive no credit. A random sample of 25 customers was chosen in UMUC MiniMart between 3:00 and 4:00 PM on a Friday afternoon. The frequency distribution below shows the distribution for checkout time (in minutes). Checkout Time (in minutes) Frequency Relative Frequency 1.0 - 1.9 4 2.0 - 2.9 0.4 3.0 - 3.9 4.0 - 4.9 5 Total 25 2. Complete the frequency table with frequency and relative frequency. (5 pts) 3. What percentage of the checkout times was at least 3 minutes? (5 pts) 4. In what class interval must the median lie? Explain your answer. (5 pts) 5. Assume that the largest observation in this dataset is 4.8. Suppose this observation were incorrectly recorded as 8.4 instead of 4.8. Will the mean increase, decrease, or remain the same? Will the median increase, decrease or remain the same? Why? (5 pts) Refer...

• STAT 200 OL4 US2 Sections Final Exam Spring 2015 Complete Solution answersA+++++++++++.docx 28 KB