Ivo Dinov
UCLA Statistics, Neurology, LONI

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STAT 13 (1a, 1b, 1c, 1d)

Introduction to Statistical Methods for the Life and Health Science

Department of Statistics

## Instructor: Ivo Dinov

Homework 1
Due Date: Wednesday, April 10, 2013

Please, submit your homework right before lecture on the due date. See the HW submission rules. On the front page include the following header.
(a) Construct a stem-and-leaf diagram of the data by hand (only for the RELIG, religiosity, variable)
(b) Construct a dotplot of the data, using SOCR Charts (Select Dot-Plot), for these variables - EDU, QOL, HI.
• (HW_1.3) The histogram below (right) shows the same data that are shown in one of the four boxplots (left). Which boxplot goes with the histogram? Explain!

• (HW_1.4)  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:
 8.1 5.6 5.9 5.9 6.2 7.4 6.3
(a) Calculate the (sample) mean and standard deviation. Explain these 2 sample measures in the context of the data.
(b) Determine the median and the interquartile range.
(c) Calculate the coefficient of variation.
(d) Replace the observation 5.9 by 3.9 and repeat parts (a) and (b). Which of the descriptive (sample) measures above display resistance to this change and which do not?

• (HW_1.5) Using the Fisher's multivariate dataset on iris sepal and petal length dataset:
(a) Determine the median and the quartiles for the Sepal-Length(cm) of the Iris-setosa genus.
(b) Determine the interquartile range of the Sepal-Length(cm) of the Iris-setosa genus.
(c) Construct a boxplot of the Sepal_Length, Sepal_Width, Petal_Length, Petal_Width  for each of the 3 genera, use SOCR Charts (Select Box-Plot).

• (HW_1.6)  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.
•  Values Frequencies Number_of_Bristles Number_of_Flies 29 2 30 0 31 1 32 1 33 2 34 6 35 9 36 11 37 12 38 18 39 13 40 10 41 15 42 10 43 2 44 3 45 3 46 1
(a) Find the Median  number of bristles.
(b) Find Q1 and Q3.
(c) Make a histogram plot of the number of bristles.
(d) Suppose the sample (number of bristles) mean is 38.45 and the sample SD is 3.20. What percentage of the observations fall within 1 SD of the mean?

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