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BioStats Sample Midterm.pdf

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Western University
Biology 2244A/B
Ben Rubin

The University of Western Ontario Biology/Stats 2244 Old midterm questions NOTE: These questions were taken from an exam offered ina previous term when a different textbook was used. In the term that this exam wasoffered the following topics were not included: counting rules (Ch 3.8) and the binomial distribution and CI’s for p (Chs. 4-3, 4-4, 5-6 & 6-2). Therefore, questions on these topics are not included in this sample exam but will appear on your midterm. Also, we used the letters Y and y as the random variable of interest throughout this exam. So, please treat Y and y as X and x, respectively to match the notation we’ve been using use this term. 1. In a large population of adults, the mean IQ is 112 with a standard deviation of 20. Suppose 200 adults are randomly selected for a market research campaign. Which of the following accurately describes the distribution of IQ in this population? A. exactly normal B. approximately N(112,20) C. approximately N(112,1.4) D. not enough information to determine 2. Refer to the previous question. What is the probability that the mean IQ of 200 randomly selected adults will be greater than 110? A. 0.079 B. 0.421 C. 0.921 D. 0.579 3. What is the definition of a random variable? A. a random number generated for random sampling B. a parameter with unknown value C. an arbitrarily selected variable D. a numerical variable whose value depends on chance 4. A group of 10 patients with end-stage renal disease were given the drug epoetin. The average hemoglobin level of the patients was 10.3 g/dLi andthe SD was 0.9 g/dLi. Construct a 99.9% confidence interval for the true mean hemoglobin level for thepopulation of all patients with end-stage renal disease. The CI is 10.3 ±______. A. 0.94 B. 1.31 C. 1.36 D. Not enough information to construct a valid interval. 1 5. Which of the following is an example of inferential logic? A. I see three dogs who all bark. Therefore, it is likely that many dogs bark. B. All dogs are mammals. Therefore, my dog, Mu, is a mammal. C. All dogs are mammals. Therefore, all mammals are dogs. D. Don’t pee in our pool. We don’t swim in your toilet. 6. In a study of milk production in sheep a researcher measured the three-month mild yield (in liters)for each of 20 ewes. The average of the 20 yields was 82.7 liters and the coefficient of variation was computed to be 24%. What is the standard deviationof the 20 yields? A. 19.8 liters B. 4.1 liters C. 3.4 liters D. 0.3 liters 7. The empirical rule states that approximately 95% of a normal curve lies within +/- 2 standard deviations of the mean. Which of the following isa more accurate percentage? A. 94.96% B. 95.44% C. 95.96% D. 97.72% 8. Select the correct statement based on the following histograms: 6 6 5 5 4 4 3 3 2 2 FREQUENCY FREQUENCY 1 1 0 2 4 6 8 10 12 0 2 4 6 8 10 12 SCORE SCORE A. The distribution on the left has a larger standarddeviation than the distribution on the right. B. The distribution on the right has a larger standard deviation than the distribution on the left. C. Both distributions have approximately the same standard deviation. D. Both distributions have approximately the same shape. 9. Intelligence quotients (IQ’s) are approximatelynormally distributed with a standard deviation of16. A random sample of three individuals have their IQ’stested and generate a sample mean of 90. Determinea 99% confidence interval for the mean IQ score. A. (73.3, 106.7) B. (66.2, 113.8) 2 C. (57.1, 122.9) D. More information is needed to determine a valid confidence interval. 10. An infant’s parents are told by a nurse that their child’s weight is at the 98 percentile when compared to the general population of healthy babies of thesame age and gender. What does this mean? A. 98% of healthy babies of the same age and gender inthe population weigh more than their child. B. 2% of healthy babies of the same age and gender inthe population weigh more than their child. C. Their child’s weight is 98% of the average weight of healthy babies of the same age and gender. D. None of the above. 11. A sample of 100 distances has a mean of 30 and a standard deviation of 6. Unfortunately, it has just been discovered that one distance was erroneously recorded as 20 when it should have been 25. Once the correction is made what will happen to the mean? A. It will definitely increase. B. It may increase. C. It may decrease. D. It will definitely decrease. 12. Birth weights at a local hospital follow a normal distribution will mean 110 oz. and standard deviation 15 oz. What is the probability that a randomly selected birth weight will be between 125 and 140 oz? A. 0.816 B. 0.636 C. 0.477 D. 0.136 13. You see some information reported in a published paper. You are interested to know the sample mean but do not see it included in the report. Ofthe following choices, which includes the least information that would allow you to determine the mean of a sample? A. A confidence interval for µ B. A confidence interval for µ and the confidence level of the interval C. A confidence interval for µ the confidence level and the sample size D. More information is needed to determine the mean ofthe sample. 14. Sickle cell disease is a painful disorder of the red blood cells. To investigate whether the drug hydroxyurea can reduce the pain, an experiment willbe conducted on eight subjects with the disorder. The researchers are going to randomly assign the drug to four of their subjects and a placebo to the other four. The number of pain episodes reported by eachsubject will then be recorded over the duration ofthe study. In this example what is the number of pain episodes? A. a response variable B. an explanatory variable C. an extraneous variable D. a normal variable 3 15. A researcher is interesting in estimating the average diameter of American sycamore trees. She measures 5 trees and a QQ plot exhibits an obviouscurved pattern. However, the QQ plot of the square root of the diameters displays a straight line. Her raw data of the diameters are: 12.4 44.8 28.2 34 41.5 Construct a 95% confidence interval for the appropriate mean. A. (20.95, 43.41) B. (4.45, 6.65) C. (16.28, 48.08) D. (3.99, 7.12) Ignore this one – we didn’t cover this paper this term: 16. The paper by Matthews et al (2008) which you read for your first lab concluded that fetal sex was related to mother’s diet during which timeframe? A. before conception B. after conception but before fetal sex was determined C. during early pregnancy (defined in the study as thefirst trimester) D. throughout the entire pregnancy 17. The mean lifespan for a sample of 5 protozoa is 22 hours. It is known that the standard deviation of all such protozoa is 2 hours. Construct a 90% confidence interval for the population mean. A. (20.5, 23.5) B. (20.9, 23.1) C. (20.2, 23.8) D. More information is needed to determine a valid confidence interval. 18. Which of the following correctly describes ? A. is the standard deviation of the sample. B. is the sampling dis
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