STAT 13

(Sec. 1a-1c)

Introduction to Statistical Methods for the Life and Health Sciences

Instructor: Ivo Dinov, Asst. Prof.

Departments of Statistics & Neurology

http://www.stat.ucla.edu/~dinov/

Due Date:

See the HW submission rules. On the front page include the following header.

(HW_7_1) In 1996 the New Zealand Consumers' Institute conducted a survey on home computer use. 7,400 subscribers to Consumer Magazine were randomly selected and sent a survey form. Of those surveyed 2,730 had a computer for personal use at home. The respondents who had a home computer were given a list of computer activities and were asked to indicate all of those that they engaged in. They were also asked to indicate the number of hours per week that they used their computer. The Consumers' Institute used the results to draw conclusions about subscribers who own a home computer. The results of the survey are given in the two tables below:

Is this survey representative of the home computer use of New Zealanders? Briefly justify your answer.
What proportion of the respondents use their computers for drawing?
What percentage of the respondents use their computers between 21 and 28 hours (inclusive) per week?
Is there any evidence to suggest from the survey that there is a significant difference between the proportion of respondents who use their computer for drawing and the proportion of respondents who use their computer for desktop publishing. Carry out a t-test to investigate this. Calculate a 95% confidence interval for the difference in these proportions. Interpret your results.

(HW_7_2) Tuberculosis (TB) is known to be a highly contagious disease. In 1995 a study was carried out on a random sample of 1074 Spanish prisoners. The study investigated factors that might be associated with the tuberculosis infection. The results follow.

Variable	PrisonersWithTuberculosis		Total Number Of Prisoners
Gender	Male	556	984
	Female	36	90
Race	White	496	886
	Gypsy	74	152
	Other	22	36
IntravenousDrugUsers	Yes	361	629
	No	231	445
HIV_Positive	Yes	186	294
	No	406	780
Re-imprisonment	Yes	272	456
	No	320	618

race

Let p_W be the proportion of White prisoners infected with TB and p_G be the proportion of Gypsy prisoners infected with TB.

\Ivo D. Dinov, Ph.D., Departments of Statistics and Neurology, UCLA School of Medicine/