STAT243 LS: Intro to Probability and Statistics Quiz 1, Feb 10, 2017 KEY

Transcription

1 STAT243 LS: Intro to Probability and Statistics Quiz 1, Feb 10, 2017 KEY This is a 50-min quiz. Students may use a page of note (front and back), and a calculator, but nothing else is allowed. 1. A researcher wants to show the distribution of times it took subjects who smoke to fall asleep. Which graphic would be the best choice? A) bar graph B) time plot C) histogram D) pie chart 2. Which graphic would best display the distribution of the top ten causes of death in the United States? A) bar graph B) time plot C) histogram D) stemplot 3. Clinical trial administrator keeps a database of information on participating subjects. Which of the following variables would be considered as quantitative? A) city B) state C) zip code D) None of the above. 4. Researchers examined a new treatment for advanced ovarian cancer in a mouse model. They created a nanoparticle-based delivery system for a suicide gene therapy to be delivered directly to the tumor cells. The grafted tumors were injected either with the new treatment or with only some buffer solution to serve as a comparison. The following is a dotplot (R calls it a stripchart) for the fold increase in tumor size after two weeks in 10 mice given buffer solution. Find the midpoint. A) 5.5 B) 6.1 C) 6.8 D) 7.0

2 Fold Increase 5. Below is a histogram of the lengths, in feet, of 44 Great White Sharks. How many sharks were shorter than or equal to 15 feet? A) 24 B) 18 C) 10 D) 20

3

4 6. The level of various substances in the blood influences our health. The following table displays available information on measurements of the level of phosphate in the blood of a patient, in milligrams of phosphate per deciliter of blood, made on 6 consecutive visits to a clinic. By accident, a value was erased but the sample mean of the 6 measurements is still available, x = 5.4. Compute the x value and sample variance of the 6 values. Hint: Consider the definition of the sample mean. x i x i x (x i x ) = = = -.2 (-.2) 2 = = -.8 (-.8) 2 =.64 x = = -.5 (-.5) 2 = =.3 (.3) 2 = = = 1 Sum = 2.06 x = x x n n = x = x = 32.4, => x = 4.9 s 2 = 2.06/5 =.412 A) (x=4.9, s 2 = 0.412) B) (x=4.9, s 2 = 0.642) C) (x=4.0, s 2 = 0.412) D) (x=4.0, s 2 = 0.912)

5 7 10. The following is a boxplot of the number of seal pubs born in Alaska from 1975 to Pups Born The boxplot shows that at least 25% of the data values are or more. A) B) C) D) 34.62

6 8. The mean value would be A) less than B) greater than but less than C) great than D) none of these is true. 9. The distribution of the number of pups born is A) Symmetric B) Skewed to the left C) Skewed to the right D) Bimodal 10. Interquartile range (IQR) would be A) less than 10 B) between 10 and 15 C) between 20 and 25 D) more than Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. About 1 in 1000 children are born with autism. In order to compare children born with autism to those not born with autism, one would use: A) a simple random sample of children. B) a retrospective study. C) a case-control study. D) a cohort study. 12. Five different brands of headache tablets were administered to 25 subjects experiencing fevers of 100 F or more. Then the number of hours of relief were recorded. Neither the subjects nor the people administering the tablets knew who received which brand of tablet. This is an experiment because: A) it used a random sample of subjects. B) it tested medications. C) the researcher controlled who received which brand of tablet. D) it was double-blind.

7 13. In an experiment on a new drug, subjects were randomly assigned to either a placebo or the active drug. In addition, the method of delivery of the drug (pill, skin patch, or nasal mist) was considered. How many factors were there in this experiment? A) 1 B) 2 C) 3 D) One hundred volunteers who suffer from depression are available for a study involving a new drug that is thought to be effective in treating depression. The researchers want to compare the new drug to the drug currently in use. It is believed that men and women may respond differently to the drugs. Which of the following would be the most appropriate design for this experiment? A) a matched pairs design B) a completely randomized design C) a completely randomized block design