2244 Sample Midterm

7/21/2019 2244 Sample Midterm

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The University of Western OntarioBiology/Stats 2244

Old midterm questions

NOTE: These questions were taken from an exam offered in a previous term when a different

textbook was used. In the term that this exam was offered 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 yourmidterm.

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 normalB. 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 selectedadults will be greater than 110?

A. 0.079B.

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 and the SD was 0.9 g/dLi. Construct a 99.9% confidence

interval for the true mean hemoglobin level for the population of all patients with end-stage renal disease.The CI is 10.3 ±______.

A. 0.94B.

1.31

C. 1.36

D. Not enough information to construct a valid interval.



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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 wascomputed to be 24%. What is the standard deviation of the 20 yields?

A. 19.8 litersB.

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 is a 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:

A. The distribution on the left has a larger standard deviation 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 approximately normally distributed with a standard deviation of 16. A

random sample of three individuals have their IQ’s tested and generate a sample mean of 90. Determine a

99% confidence interval for the mean IQ score.

A.

(73.3, 106.7)

B. (66.2, 113.8)

0 2 4 6 8 10

1

2

3

45

12

6

F R E Q U E N C Y

SCORE

1

2

3

45

6

F R E Q U E N C Y

0 2 4 6 8 10 12SCORE



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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 98th

percentile when comparedto the general population of healthy babies of the same age and gender. What does this mean?

A. 98% of healthy babies of the same age and gender in the population weigh more than their child.B.

2% of healthy babies of the same age and gender in the 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. 0.816B.

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. Of the 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 sizeD.

More information is needed to determine the mean of the sample.

14. Sickle cell disease is a painful disorder of the red blood cells. To investigate whether the drughydroxyurea can reduce the pain, an experiment will be 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 each subject will then be recorded over the duration of the

study. In this example what is the number of pain episodes?

A. a response variable

B. an explanatory variableC.

an extraneous variable

D.

a normal variable



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15. A researcher is interesting in estimating the average diameter of American sycamore trees. Shemeasures 5 trees and a QQ plot exhibits an obvious curved 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 41.5Construct 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 determinedC.

during early pregnancy (defined in the study as the first 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 distribution of the standard deviation.

C. is the standard deviation of the sample mean.

D.

is the standard error of the sample mean.

19. A random sample is taken from a N(0,1) population. Which of the following observations would beconsidered an outlier?

A. -2B. 0

C. 3.5

D. More than one of the above



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20. Researchers with to determine if a new experimental medication will reduce the symptoms ofallergy sufferers without causing drowsiness. To investigate this question, the researchers give

the new medication to 50 adult volunteers who suffer from allergies. 44 of these volunteers

report a significant reduction in their allergy symptoms without any drowsiness. This study couldbe improved by _______.

A. including people who do not suffer from allergies in the study to represent a morediverse population

B. repeating the study with only the 44 people who reported a significant reduction in theirallergy symptoms without any drowsiness, and giving them a higher dosage this time.

C. using a control group.D. all of the above.

21. What advantage do experiments have over observational studies?

A. They are easier to conduct.

B. The do not require replication.C.

They can use sample data whereas observational studies require population data.

D.

They can demonstrate causality.

22. An agricultural researcher plants 100 plots with a new variety of corn. The average yield for these

plots is 150= y bushels per acre. Assume that the yield per acre for the new variety of corn has unknown

mean,µ, and standard deviation σ=20 bushels per acre. Find the 90% confidence interval for µ.

A.

(148, 152)

B. (146.71, 153.29)

C. (146.08, 153.92)

D.

Cannot compute a valid interval here.

23. Refer to the previous question. Assuming a valid confidence interval was possible in this situation,

which of the following would produce a more precise confidence interval than a 90% confidence interval?

A. Plant only 20 plots rather than 100.

B. Plant 500 plots rather than 100.

C.

Compute a 99% confidence interval rather than a 90% confidence interval.

D. None of the above.

24. Suppose a student writing a midterm knows 50% of the material covered by the exam. Therefore, for a

given question, there is a 0.50 probability that he knows the answer. Suppose he randomly chooses one of

the four options for the questions to which he does not know the answer. What is the probability that he’ll

get the first question on the exam correct?

A. 0.500

B. 0.625

C.

0.750

D. Not enough information to compute.

25. What is the Z score of the first quartile of a normal distribution?

A. -0.75 B. -0.67 C. -0.25 D. +0.25



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26. Suppose that the daily high temperature in a certain City has ! = 27 degrees C and " = 3 degrees C

and is approximately normal. What is the approximate probability that on a randomly selected day in July

the high temperature will be between 20 and 30 degrees C?

A.

82%

B.

83%

C. 84%

D. 85%

27. In SPSS what is the effect of choosing to “Split Data” and “organize by groups”

A.

The data file will be divided into more than one file.

B. The data file will be composed of more than one worksheet.

C. All subsequent analyses will be conducted more than once.

D.

The data will be sorted.

28. If you are given Q1 = 3, Q2 = 6 and that the interquartile range is 7, what is the third quartile?

A.

3

B.

10C. 13

D.

Not enough information to compute.

29. Suppose the heights of 15-year-old Canadian boys, in inches, are normally distributed with mean µ

and standard deviation σ = 2.4. I randomly select four boys and measure their heights:

63 in 69 in 62 in 66 in. Based on this sample, a 99% confidence interval for µ, in inches, is

65±_______.

A. 1.55

B.

2.35

C.

3.09D. 4.07

30. 33% of the N (3, ") density curve is below 1. Find ".

A. 0.37

B.

0.88

C. 1.32

D. 4.55



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31. The histogram below gives the distribution of the heights of 64 students in a biology course.

Which of the following statement is correct?

A. Approximately half the students have heights between 62 and 65 inches.

B. The shape of this height distribution is symmetric.

C.

The tallest person must have a height of at least 79 inches.D. None of the above statements are correct.

32. Refer to the previous question. If you wanted to construct a density histogram of this height data

instead, which of the following statements are correct?

A. The bar for the 62 to 65 class would have a height of approximately 0.09 in the density histogram.

B. The density histogram will have a slightly different shape than the frequency histogram.

C. The heights of all the bars in the density histogram will add up to 1.

D. More than 1 of the above statements are correct.

33. The 95% confidence interval for the mean concentration of NO2 in the air of a certain city is (35 ppm,65 ppm). Does the 99% confidence interval based on the same data contain 70 ppm?

A. Definitely yes.

B. Maybe.

C.

Definitely no.

34. If the dots on an SPSS Q-Q plot form a curve which goes up quickly and then levels off, this

indicates what type of distribution

A. left-skewed

B.

right-skewedC.

normal

D. symmetrical but non-normal



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35. The daily recommended intake of potassium is 4000 mg for adults. A clinician is interested in finding

out whether Canadians are getting enough potassium. A random sample of 22 people had an average daily

intake of 3880 mg and standard deviation 150 mg. What is the standard error of the sample mean?

A.

6.81

B.

31.98

C. 4.69

D. 150.00

36. A statistics instructor constructed a boxplot of midterm grades. What other graphical summary would

be appropriate?

A. bar chart

B. frequency table

C. histogram

D. none of the above.

37. To study the difference in reaction time between people’s hands which of the following experimental

designs would be preferable?

A.

A paired-samples design comparing left vs. right handsB. A paired-samples design comparing dominant vs. non-dominant hands

C.

An independent samples design comparing left vs. right hands

D. An independent samples design comparing dominant vs. non-dominant hands

38. Select the words appropriate for the following blanks: ____________ are to samples as ___________

are to populations.

A. parameters, statistics

B. random variables, data

C. data, random variables

D. statistics, parameters

39. If knowledge that an event A has occurred implies that a second event B cannot occur, then which

term correctly describes events A and B?

A. independent

B.

disjoint

C. random

D. None of the above terms are correct.

40. A zoologist measured tail length of 86 deermice (Peromyscus). He calculated a 95% confidence

interval for the mean to be (59.77 mm, 61.09 mm). Which of the following statements is/are true?

A.

We are 95% confident that the average tail length of the population of all deermice is between

59.77 and 61.09.

B. We are 95% confident that the average tail length of the 86 mice in the sample is between 59.77

and 61.09.

C. There is a 95% chance that the average tail length of the population of all deermice is between

59.77 and 61.09.

D.

More than one of the above statements are true.

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2244 Sample Midterm