BIOSTATS PRACTICE TEST
QUESTION 1 (3 points)
Researchers examined literacy and magazine reading in Tasmanian adults. They interviewed 300 people and found that 19 people were illiterate and 281people were literate. Of the 281 literate people, the majority (84.2%) read magazines once a week, spending an average of 1.2 hours reading them per week.
For this study, please match the items with their correct concept.
ITEMS:
What is the population?
1.2 hours is an example of what?
The 300 interviewed people are an example of what?
CORRECT CONCEPT:
a. population
b. sample
c. parameter
d. Tasmanian adults
e. statistic
f. 281 literate people
g. 300 people
h. 19/300 is an underestimation of the number of illiterate people in Tasmania
QUESTION 2
In a study of the oral home care practice and reasons for seeking dental care among individuals with angina, a researcher studied 30 subjects with angina. The oral hygiene status of all subjects was examined using plaque index scores that range from 0 to 3. Variables are Pindex: plaque index score; Gender: M=Male, F=Female. The data are available in the file, PlaqueIndexScore2.csv, and are as follows:
Pindex Gender Angina
1.17 M 1
2.50 M 2
2.33 M 3
1.67 M 1
1.33 M 2
2.17 M 3
2.40 M 1
1.5 M 2
2.5 M 3
1.67 M 1
1.5 M 2
1.5 M 3
1.5 M 1
1.33 M 2
2.77 M 3
2.17 F 1
0.90 F 2
1.67 F 3
0.33 F 1
2.67 F 2
0.5 F 3
0.83 F 1
0.33 F 2
1 F 3
0.83 F 1
0.43 F 2
1.17 F 3
1.67 F 1
1.17 F 2
2.60 F 3
Using R Commander, calculate the
first:
second:
and third:
quartiles for plaque index scores. Present each number to TWO decimal places.
QUESTION 3
Using R Commander and PlaqueIndexScore2.csv, calculate the mean plaque index score for Males. Calculate your answer to TWO decimal places: X.XX and no other extraneous text.
QUESTION 4
Using R Commander and PlaqueIndexScore2.csv, calculate the SD of plaque index score for Females. Calculate your answer to TWO decimal places: X.XX and no other extraneous text.
QUESTION 5
Which figure represents the distribution of males’ plaque index scores from the data, PlaqueIndexScore2.csv?
1. Figure 1
2.Figure 2
3. Figure 3
4. Figure 4
QUESTION 6
Assume that we can use the Normal distribution to calculate a 80% Confidence Interval for the plaque index score for all 30 individuals in the study.
Using R Commander and PlaqueIndexScore2.csv, provide the lower value of the 80% confidence interval for mean plaque index score for all individuals in the study. Calculate your answer to TWO decimal places: X.XX and no other extraneous text.
QUESTION 7
Assume that we can use the Normal distribution to calculate a 80% Confidence Interval for the plaque index score for all 30 individuals in the study.
Using R Commander and PlaqueIndexScore2.csv, provide the upper value of the 80% confidence interval for mean plaque index score for all individuals in the study. Calculate your answer to TWO decimal places: X.XX and no other extraneous text.
QUESTION
For the plaque score data set, please choose the answer which best describes your interpretation of the 80% confidence interval for the mean plaque score calculated above?
a) There is a probability of 0.8 that the true sample mean is in the 80% confidence interval.
b) The confidence interval contains the true sample mean with a probability of 0.8.
c) The confidence interval contains the true population mean with a probability of 0.8.
d) There is a probability of 0.8 that the true population mean is in the 80% confidence interval.
QUESTION 9
Match the variable to its variable type. Answer items can be used more than once.
Variable:
_Number of premature babies born at Royal Brisbane Hospital
_Weights of babies (in grams) born at Royal Brisbane Hospital during a year
_Range of motion of elbow joint (none, limited, full) of students enrolled in a university
_Under-arm temperature (degrees C) of day-old infants born in a hospital
_Number of cigarettes smoked in a week (none, 1-4, 5-10, 11+)
_Country of origin (Australia, other English-speaking country, non-English speaking country)
Variable type:
a) nominal
b) continuous
c) qualitative
d) ordinal
e) discrete
QUESTION 10
In the US, one question that the General Social Survey asks is whether you agree or disagree with the following statement: “It is more important for a wife to help a husband’s career that to have one herself”. In 2010, 396 out of 1907 respondents agreed. Calculate the best estimate of the proportion of respondents who agreed with the question, reporting your answer to two decimal places so that the number looks like X.XX :
QUESTION 11
For the question about a wife’s career above, a 90% confidence interval is:
a) (0.189, 0.226)
b) (0.196, 0.220)
c) (0.192, 0.223)
d) (0.184, 0.232)
QUESTION 12
In a normal distribution, what z-score separates the highest 25% of the scores from the rest of the distribution?
a) z = 0.25
b) z = 2.05
c) z = +0.67
d) z = -0.67
QUESTION 13
A list of 5 pulse rates is: 53, 80, 74, 64, 70. What is the third quartile for this list?
a) 73
b) 80
c) 70
d) 74
e) 76
QUESTION 14
A study in Australia of 500 diabetes patients who tightly controlled their blood pressure showed a 41% reduction (proportion reduction=0.41) in the risk of adverse effects with a 95% confidence interval of 37%-45% (or 0.37-0.45). Suppose a similar study was conducted in USA which has a population about 15 times that of Australia. Also suppose that the study yielded a similar reduction but had 2000 participants. The resulting 95% confidence intervals for the US study will be:
a) about 1/4 as wide as the Australian interval
b) about 4 times as wide as the Australian interval
c) about 1/2 as wide as the Australian interval
d) about 15 times as wide as the Australian interval
e) the same size as the Australian interval
f) about twice as wide as the Australian interval
QUESTION 15
A set of exam scores has mean = 50 and standard deviation = 15. The instructor would like to transform the scores into a standardised distribution with mean = 100 and standard deviation = 21. Find the transformed value for X = 45 from the original population.
Type your answer with NO decimal places or any other extraneous text. (ie 41 would be marked correctly whereas 41.0 would be marked incorrectly. Similarly, X=41 which has extraneous text would be marked incorrectly.)
QUESTION 16
Which one of these statistics is not affected by outliers?
a. Range
b. Interquartile range
c. Standard Deviation
d. Mean
QUESTION 17
A sample of university students has an average weight of 74.6 kg. Which of the following is an impossible value for the standard deviation?
a) 74.6
b) 12.4
c) -12.4
d) 0.0
QUESTION 18
The mean, median and mode can never all be the same.
True
False
QUESTION 19
The mean score of an assessment for all subjects in a medical study was 2.77. A subject with a score of 2.0 wants to know her relative standing in relation to the mean score. A numerical summary that would be useful for this purpose is the
a) median
b) standard deviation
c) the number of subjects in the study
d) interquartile range
QUESTION 20
The median of a Normal distribution enables us to calculate:
a) The size of the variable
b) The location of the peak of the distribution
c) The total area under the Normal curve
d) None of the above
QUESTION 21
In a survey of 750 Americans conducted by the Gallop organisation, 24% indicated a belief in reincarnation. Using the appropriate methods to predict the confidence interval for all Americans, the percentage believing in reincarnation falls between 21% and 27%. The prediction is an example of
a. descriptive statistics
b. a data file
c. inferential statistics
d. designing a study
QUESTION 22
A Normal distribution will have (SELECT ALL THAT APPLY):
a) A bell shaped curve
b) Exactly 50% of the distribution will be on either side of the mean
c) The mean and median will be identical
d) A mean of zero and a standard deviation of 1
QUESTION 23
Which is the process of gathering evidence supporting inferences based test scores?
a) Prediction
b) Validation
c) Validity
d) Reliability
QUESTION 24
Which of the following statements accurately describes test-retest reliability?
a) Measure of consistency with which a test measures a single construct or concept
b) Measure of degree of agreement between two or more scorers, judges, or raters
c) Measure of consistency of scores obtained from two equivalent halves of the same test
d) Measure of consistency of test scores over time
