STAT 310 – Intermediate Statistics TAKE HOME MIDTERM EXAM (40 pts.)
For each problem conduct a thorough analysis to address the question of interest to the researchers. Be sure state conclusions in the context of the question asked, i.e. “Reject Ho” is NOT sufficient. Use CI’s where appropriate to quantify significant effects and be sure to interpret them. For some of the problems there is possibly more than method that could be used, therefore you will have to choose the method of analysis you feel is most appropriate for the given data making sure you justify your choice.
1 – Neuroticism and Smoking Habits
A psychology research team administered a test designed to measure neuroticism in four groups of subjects who differed on the basis of their smoking habits. The resulting data is presented below.
Research question: Is there a difference in the neuroticism level among the four groups?
Data: Neuroticism scores of subjects classified according to smoking habits
Nonsmokers: 7.6 7.7 7.5 7.8 7.6 7.3 7.1 8.0 7.5 8.0
Light smokers: 8.9 8.2 8.1 8.0 8.6 8.6 8.6 8.4
Med. smokers: 8.0 8.8 8.7 8.6 9.0 8.8 8.5
Heavy smokers: 9.9 9.1 9.8 9.8 9.9 9.6 9.2 9.8
a) Use an appropriate statistical method to answer the question of interest. Summarize your findings. (4 pts.)
b) If there are differences in the neuroticism levels among the four groups, which groups significantly differ? Discuss your results. (4 pts.)
2 – Social Worker Appearance and Rapport with Male Juvenile
Offenders
In a study of factors related to the development of rapport between male juvenile offenders and social workers, two types of interview were conducted with each of 12 subjects. In the first interview the social worker wore a beard and long hair, dressed in a very casual manner, and used the language of the youth subculture. Each juvenile offender was then interviewed by another male social worker who was about the same age as the first, whose dress, language, and appearance identified him as a member of the “the Establishment”. The interviews were otherwise conducted in as similar a manner as possible. After each interview, subjects rated the interviewer on the basis of how well they would like to have him as a permanent counselor (1 = would very much want him, 2 = would want him, 3 = would not want him, and 4 = would very much not want him). The results are shown in the table below.
Research question: Is there evidence to suggest that social workers who are perceived as antiestablishment are more popular with juvenile offenders?
Data: Juvenile offenders’ ratings of two social workers
Subject / Antiestablishmentsocial worker / Establishment
social worker
1 / 1 / 4
2 / 2 / 2
3 / 2 / 1
4 / 1 / 3
5 / 1 / 4
6 / 2 / 4
7 / 2 / 3
8 / 1 / 2
9 / 1 / 4
10 / 1 / 3
11 / 2 / 3
12 / 2 / 4
Use an appropriate statistical method to answer the question of interest. Summarize your findings. (4 pts.)
3 – Negative Symptoms and Alzheimer’s Disease
Reichmann et al. in their paper “Negative Symptoms in Alzheimer’s Disease”, American Journal of Psychiatry, 153, (1996) report on the results of a study whose purpose was to demonstrate that negative symptoms are prominent in patients with Alzheimer’s disease and are distinct from depression. The data in the file Alzheimers.JMP are scores made on the Scale of the Assessment of Negative Symptoms (SANS) in Alzheimer’s Disease by patients with Alzheimer’s disease (PT) and normal elderly, cognitively intact, comparison subjects (C).
Research question: Is there evidence to suggest that individuals with Alzheimer’s have higher SANS scores than the cognitively intact elderly individuals?
a) Use appropriate statistical methods to answer the question of interest and summarize your findings. (4 pts.)
b) Quantify the size of the difference in mean SANS scores between the two groups with a confidence interval. Summarize/interpret the results. (3 pts.)
4 – Use of Weights to Control Hand Tremors of Parkinson’s Patients
The goal of a study reported by Meshack and Norman in “ A Randomized Controlled Trial of the Effects of Weights on Amplitude and Frequency of Postural Hand Tremors in People with Parkison’s Disease”, Clinical Rehabilitation, 16 (2003), 481-492 was to evaluate the effects of weights on postural hand tremor related to self-feeding in subjects with Parkinson’s disease (PD). Each of the 16 subjects had the tremor amplitude measure (in mm) under three experimental conditions: holding a built-up spoon (108 g), holding a weight spoon (248 g), and holding the built-up spoon while wearing a weighted wrist cuff (470 g). The data are contained in the file Parkisons.JMP.
Research question: Can one conclude on the basis of these data that the three experimental conditions, on the average, have different effects on tremor amplitude?
a) What type of experimental designs was used in conducting this study? (1 pt.)
b) Use appropriate statistical methods to answer the question of interest and summarize your findings. If there are differences in the tremor amplitudes between the conditions be sure to identify and quantify them. (5 pts.)
5 – National Longitudinal Survey of Youth (NLSY) ~ Demographics of the respondent and age at which respondent had first child
Datafile: Demographics First Child.JMP
Background: The NLSY79 is a nationally representative sample of 12,686 young men and women who were 14-22 years old when they were first surveyed in 1979. These individuals were interviewed annually through 1994 and are currently interviewed on a biennial basis. Since their first interview, many of the respondents have made transitions from school to work, and from their parents' homes to being parents and homeowners. These data provide researchers an opportunity to study a large sample that represents American men and women born in the 1950s and 1960s, and living in the United States in 1979.
A key feature of this survey is that it gathers information in an event history format, in which dates are collected for the beginning and ending of important life events. Labor force activity is detailed in this manner. Information includes the start and stop dates for each job held since the last interview, periods in which individuals are not working but still with an employer (called within-job gaps), and labor market activities (looking for work, out of the labor force) during gaps between jobs. Because individuals' work histories are collected in this manner, measures of actual labor market experience, tenure with a specific employer, and employer mobility are easily calculated. Additional information collected in the event-history format includes marital status, fertility, and participation in government assistance programs such as unemployment insurance and Aid to Families with Dependent Children (AFDC).
Although a primary focus of the NLSY79 survey is labor force behavior, the content of the survey is considerably broader. The survey contains an expansive set of questions ranging from child-care costs to welfare receipt. For example, the survey includes detailed questions on educational attainment, training investments, income and assets, health conditions, workplace injuries, insurance coverage, alcohol and substance abuse, sexual activity, and marital and fertility histories. Additional labor force information includes hours worked, earnings, occupation, industry, benefits, and other specific job characteristics.
These data consist of a small portion of the NLSY79 database and contains the following variables:
· Educ94 = highest education level of the respondent in 1994.
· Sex = gender of the respondent
· Race = recorded as Black, Other, White
· Age at 1st Birth = age at which respondent had their first child (yrs.)
Use appropriate statistics methods to address the following questions. (5 pts. each)
a) Does the age at which respondent had their first child differ across groups defined by education level? If so, discuss differences. Give a discussion of the results for a general audience.
b) Are there differences in the age at which the respondent had their first child across gender? Is so, quantify the difference. Give a discussion of the results for a general audience.
c) Does the age at which respondent had their first child differ across groups defined by race? If so, discuss differences. Give a discussion of the results for a general audience.