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statistics econometrics

Questions and Answers of Statistics Econometrics

1 A null hypothesis is given as “for the sample of general dental practitioners in New York the mean number of patients treated per day is signifi cantly different from 40.” Is this an
3 A national chain of chemist stores sells a particular brand of mouthwash.Following a reduction of 10% in the price of the mouthwash, average weekly sales per store rose from 35 to 41 bottles per
2 Explain with an example from dentistry what is meant by the term“paired data.”
1 The standard deviation and standard error are both measures of variation. How do they differ from each other?
4 A study of young adults investigated the validity of self- reported dental agenesis (DA) using a guided questionnaire. The responses were then compared with childhood dental records and
3 A diagnostic study involved the consideration of suspicious oral mucosal lesions by clinical assessment and by “gold standard”histopathology (Güneri et al. 2011). Of the 13 lesions
2 What are the likely consequences of a diagnostic test for which unaffected individuals must never receive a positive screening result?
2 The following 95% confi dence intervals represent the difference in the percentage with gingivitis in a comparison of male and female young adults. The null hypothesis is that the true percentages
1 Consider the assumptions made in using one- way analysis of variance, listed in the options. For each of the scenarios described below, select the assumption that is most obviously
2 An investigation was conducted on patients aged less than 21 regarding who, if anyone, accompanied them to their appointment at a dental hospital (family member, a friend, attended alone). The fi
3 In the investigation of the literature on dental caries in children conducted by Hayden et al. (2013), the studies listed for the metaanalysis of primary teeth were not exactly the same as those
1 Give reasons as to why a journal article might not be identifi ed in a database search.
3 If a power of 0.9 is required, the sample size requirement can be estimated using the rule of 21. Explain how this rule operates in simple terms. What do the rules of 16 and 21 indicate about the
2 Use the rule of 16 to estimate the sample- size requirement where the two means in the alternative hypothesis are 5 and 3, the assumed standard deviation is 2, and a power of 0.8 is required.
1 Give three reasons why the distribution of observations from a sample will not have an exact Normal distribution.
1 Explain why a study design that allows for a power of 0.5 would be considered unacceptable.
4 Sketch a scatter diagram for which Spearman’s rank correlation is around –1 but Pearson’s correlation will be closer to zero.
3 Write down a set of observations containing censored values to which the straightforward method of ranking can be applied.
2 A group of adults aged 18–30 years living in London is to be compared with a similar group living in Edinburgh, using the DMFT score. Name an appropriate statistical test for analyzing the two
1 Explain why a simple logarithmic (log) transformation cannot be applied to the data in Example 10.3 showing change in salivary buffering capacity pH.
4 A school- based study was conducted in North Carolina, US into the relationship between untreated decayed primary teeth in kindergarten children (aged around fi ve years) and low household income
3 Chance- corrected agreement can be close to zero when the observed agreement is high, say 90%. Using an example from dentistry, explain how this could arise.
2 Why does an association between two variables not necessarily imply causation? Illustrate with an example from dentistry.
1 What is the most likely value for Pearson’s correlation coeffi cient for the following descriptions of scatter diagrams?Options:(a) 0 (b) –0.9 (c) 0.4 (d) 0.8 (e) 1 (i) Variables seem to be
1 Explain what is meant by positive predictive value in the context of screening for dental caries with a probe, against a bite- wing radiograph.
4 cannot be Normal?
3 Why is it that in a population of adults a distribution of the number of teeth remaining with a mean of 30 and a standard deviation of
2 Mary thinks that Joan might regard the study as less of an imposition if every sixth patient is entered into the study. Should this suggestion be made to Joan?
1 Jon, Mary’s former dental public health tutor, works in a large private dental practice located in an affl uent area on the edge of Birmingham. Five years ago he conducted a study using the same
3 In a study undertaken in a large town on attitudes to dental care, why will selection of names from the local telephone directory lead to sampling bias?
2 Describe how in a dental practice a systematic sample could be drawn from the patients arriving for treatment. Give one advantage and one disadvantage in using this method of sampling rather than
1 Explain, using an example from dentistry, what is meant by a simple random sample. Why is this type of sample not always representative of the population from which it is drawn?
3 Why might a cohort study be an unsuitable design for an undergraduate student project?
2 Explain why in a case- control study it is generally not possible to match cases with controls on age, gender, socioeconomic group, ethnicity, and the dental practice where the patient is
1 Select the most appropriate study design for investigating the topics given below.Options:(a) Case- control study(b) Cohort study(c) Cross- sectional study(d) Crossover trial(i) Wisdom teeth
4 Describe how a patient and public involvement group might contribute to an investigation into dental care provision for older people.
3 List three ways in which bias may arise in a community study of dental needs. Select one and suggest how the bias could be reduced.
2 Explain why ethical approval is required before project grants are released by research- funding organizations.
1 In a practice data set the following information is found in the records of a woman aged 35 years. What is the most likely interpretation of each value?Options:(a) Missing value indicator(b)
4 If you are a qualifi ed dentist, refl ect on how statistical ideas might be relevant to your own CPD. You might fi nd it illuminating to repeat the exercise after having worked through this text!
3 Describe using examples two ways in which the knowledge of statistical procedures can be useful to the dental practitioner.
2 The type of dental treatment that a patient receives could be classifi ed as either a nominal or an ordered variable. Explain using an example why this is the case.
3 When Mary discusses her project with Jon, he suggests a crossover design in which each patient uses the alternative solution at his or her following visit. Is this good advice?
1 Using the table below, match each variable to its type.Options:(a) Binary(b) Nominal(c) Ordered(d) Whole number quantitative(e) Continuous quantitative Patient number Gender Exact age (years)Number
2 A dentist leaves work each day between 5.30 pm and 6 pm such that any departure time within this interval is equally likely. She notes down these times over a three- month period. Is the Normal
3 Is it ethical to collect information from individuals on variables that are unlikely to be analyzed in a study?
2 Explain why neglecting to estimate the sample size required for a proposed study can be considered unethical. Give one way in which the researcher may obtain information that will assist in the
1 Select the most appropriate description of the consent obtained in the situations below.Options:(a) Positive consent(b) Passive consent(c) No consent(i) As part of a research project, children
12 The study shows that 65% of patients using Xellent and 85% of patients using Ynot were either very satisfi ed or satisfi ed with their treatment. Should Mary change to using Ynot?
11 Peter believes that this study is likely to be unrepresentative of the local community in which Mary’s practice is located. Do you think that he is correct?
10 Mary has doubts as to whether the study will fully refl ect the population of patients on her list. Are these justifi ed?
9 Joan gradually becomes more enthusiastic but she does think that children involved may pose particular problems for the study.Should this be a concern?
8 Initially it was thought that patients should complete the questionnaire before leaving the premises. It could be reasoned, however, that patients might not feel well enough to complete the
7 Hita suggests that patients should not be told about the study in advance but be handed the questionnaire following treatment. Is this good practice?
3 In a study of the attitudes in the American dental profession towards the Medicaid scheme for affordable care targeted at those with a low income, 651 dentists based in Iowa were asked whether they
6 Mary intends to allocate patients to either Xellent or Ynot on the toss of a coin, the sequence being determined in advance. Should she do this?
5 At present Ynot solution has a rather striking orange color, but the manufacturers have stated that in two months’ time it will be available in the more traditional pink. Should Mary wait until
4 Refl ecting on Jon’s advice, Mary wonders whether matching similar patients might be worth considering. Would matching be helpful here?
Suppose that the damage award favored by individual potential jurors in a particular personal injury case can be described by a normal distribution with a mean of \(\$ 5,000,000\) and a standard
It has been reported that 30 percent of all couples who adopt a child because of troubles conceiving a child eventually do conceive a child after the adoption, suggesting that adoption makes
A study in one state compared the traffic fatality rates (number of fatalities per miles driven) on highways with 55, 65, and 75 miles per hour speed limits. They found that highways with a 75 mph
How might a statistician challenge this argument that appeared The New York Times [10] in January 2014?Punishment and surveillance by itself causes people to withdraw from political
A classic test lets a monkey choose M&Ms until the researcher identifies three colors (say blue, red, and green) that the monkey seems to prefer about equally. The monkey is then offered a choice
J. B. Rhine’s book New Frontiers of the Mind reported results from his ESP experiments. The New York Times science editor was enthusiastic. He noted that some people dismiss Rhine’s results by
Explain why this is misleading: In 70 percent of all traffic accidents, the driver is less than 10 miles from home. These data show that drivers who are close to home feel safe and tend to relax and
In the gambling game Chuck-A-Luck, a player can bet \($1\) on any number from 1 to 6. Three dice are thrown and the payoff depends on the number of times the selected number appears. For example, if
A routine examination discovers a lump in a female patient’s breast. Only 1 out of 100 such lumps turns out to be malignant, but, to be safe, the doctor orders a mammogram X-ray test. If the lump
You are going to do an experiment in which you roll several six-sided dice and record the sum of the numbers on these dice. You will repeat this experiment several times and make a histogram of the
Use the data in Table 3.2 to calculate the annual rate of increase in the CPI over the 14-year period from December 2000 to December 2014.Table 3.2 1981 8.9 1998 1.6 1982 3.8 1999 2.7 1983 3.8 2000
In Little League baseball, the highest level is the majors and the next highest level is the minors. In the 2013 season, Claremont Little League had enough players to form six majors teams and six
In a computer game, the player is shown (in random order) a sequence of characters that are yellow, green, blue, red, or black. The characters are themselves:(a) Neutral (OOOOO written in
A study of the effect of college education on income used 1990 and 2010 US Census data. The study looked at: (a) women in the 1990 Census who were between 28 and 32 years old and were also the first
Which of these data are categorical and which are numerical?a. A cell phone’s brand.b. A cell phone’s estimated battery life.c. A cell phone’s screen size.d. A cell phone’s carrier.

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