1 The common fruit fly Drosophila melanogaster is the most studied organism in genetic research because it is small, is easy to grow and reproduces rapidly. The length of the thorax (where the wings and legs attach) in a population of male fruit flies is approximately Normal with a mean of 0.8 millimetres (mm) and a standard deviation of 0.078 mm.

What proportion have thorax lengths between 0.6 mm and 0.9 mm?

2 The heights of women aged 20-29 follow approximately the N(64.2, 2.8) distribution. Men the same age have heights distributed as N(69.4, 3.0). What percent of women aged 20 to 29 are taller than the mean height of men aged 20-29? [3 marks]

3 Suppose we want our academic integrity sample to mirror the proportion of freshmen, sophomore, junior, and senior students in the overall college population and that we would like to select a sample size of 200 students. Freshmen, sophomores, junior and senior comprise 30%, 25%, 35% and 10% of the student population, respectively.

a Calculate the size of each stratum in our sample, based on its percentage relative to the population. [2 marks]

b We can then apply the simple random or systematic sampling methods to select the students from each group. Why would we go through the trouble of using stratified sampling versus simple random or systematic sampling? 4 Suppose we are interested in estimating the malaria rate in a densely tropical portion of rural Indonesia. We learn that that are 30 villages in that part of the Indonesian jungle, each more or less similar to the next. Our goal is to test 150 individuals for malaria. What sampling method should be employed? Why?

5 Identify the type of sampling technique for each of the following: [5 marks]

a. The first Monday of each month, I ask my customers who come to my store to fill out a satisfaction survey.

b. I randomly select four stores in a mall and ask each customer in those stores about his or her opinion of the latest health care legislation.

c. I position myself on a busy intersection of a city street and ask people what their opinions are of a local sports team.

d. Sixty percent of the students attending my college are female. I construct a random sample that consists of 60% females from the student population to ask what their opinions are of the college's food service.

e. Using computer software, I randomly select 20 employees to participate in a job satisfaction survey.

6. Researchers collected data to examine the relationship between air pollutants and preterm births in Southern California. During the study air pollution levels were measured by air quality monitoring stations. Length of gestation data were collected on 143,196 births between the years 1989 and 1993, and air pollution exposure during gestation was calculated for each birth. Identify the population of interest and the sample in this study. [2 marks]

7. The General Social Survey asked the question, "After an average workday,

about how many hours do you have to relax or pursue activities that you enjoy?" to a random sample of 1,155 Americans. The average relaxing time was found to be 1.65 hours. Determine which of the following is a variable, a sample statistic (value calculated based on the observed sample), or a population parameter. [3 marks]

(a) Number of hours spent relaxing after an average workday.

(b) 1.65.

(c) Average number of hours all Americans spend relaxing after an average workday.