IVO D. DINOV's Home Page

Ivo Dinov
UCLA Statistics, Neurology, LONI, Math/PIC

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STAT 13 (1a, 1b, 1c)	*Introduction to Statistical Methods for the Life and Health Science*
Department of Statistics	Instructor: Ivo Dinov
Homework 1	Due Date: Monday, Oct. 08, 2007

Please, submit your homework right beofre lecture on the due date. See the HW submission rules. On the front page include the following header.

(HW_1) Do these problems from pages 24-67, Samuels & Witmer's text Statistics for the Life Sciences, Prentice Hall (2003):

2.7: A dendritic tree is a branched structure that emanates from the body of a nerve cell. As part of a study of brain development, 36 nerve cells were taken from the brains of newborn guinea pigs. The investigators counted the number of dendritic branch segments emanating from each nerve cell. The numbers were as follows:

23	30	54	28	31	29	34	35	30
27	21	43	51	35	51	49	35	24
26	29	21	29	37	27	28	33	33
23	37	27	40	48	41	20	30	57

(a) Construct a stem-and-leaf diagram of the data.
(b) Construct a dotplot of the data.

2.8: Consider the data presented in Exercise 2.7. Construct a frequency distribution and display it as a table and as a histogram.

2.36: The histogram below shows the same data that are shown in one of the four boxplots. Which boxplot goes with the histogram? Explain!

2.46: Dopamine is a chemical that plays a role in the transmission of signals in the brain. A pharmacologist measured the amount of dopamine in the brain of each of seven rats. The dopamine levels (nmol/g) were as follows:

6.8 5.3 6.0 5.9 6.8 7.4 6.2

(a) Calculate the mean and standard deviation.
(b) Determine the median and the interquartile range.
(c) Calculate the coefficient of variation.
(d) Replace the observation 7.4 by 10.4 and repeat parts (a) and (b). Which of the descriptive measures display resistance and which do not?

2.63: Here are the 20 measurements of preening time reported in Exercise 2.12:

34	24	10	16	52
76	33	31	46	24
18	26	57	32	25
48	22	48	29	19

(a) Determine the median and the quartiles.
(b) Determine the interquartile range.
(c) Construct a (modified) boxplot of the data.

2.73: A geneticist counted the number of bristles on a certain region of the abdomen of the fruitfly Drosophila melanogaster. The results for 119 individual fruitflies
are shown in the table below.

Number of Bristles	29	30	31	32	33	34	35	36	37	38	39	40	41	42	43	44	45	46
Number of Flies	1	0	1	2	2	6	9	11	12	18	13	10	15	10	2	2	3	2

(a) Find the Median number of bristles.
(b) Find Q1 and Q3.
(c) Make a boxplot of the data.
(d) The smaple mean is 38.45 and the sample SD is 3.20. What percentage of the observations fall within 1 SD of the mean?

Ivo Dinov's Home

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23	30	54	28	31	29	34	35	30
27	21	43	51	35	51	49	35	24
26	29	21	29	37	27	28	33	33
23	37	27	40	48	41	20	30	57

23	30	54	28	31	29	34	35	30
27	21	43	51	35	51	49	35	24
26	29	21	29	37	27	28	33	33
23	37	27	40	48	41	20	30	57

Instructor: Ivo Dinov

23	30	54	28	31	29	34	35	30
27	21	43	51	35	51	49	35	24
26	29	21	29	37	27	28	33	33
23	37	27	40	48	41	20	30	57