Introduction 1

CHAPTER 1 ………………………………………………………….. Introduction

1.2 a. The object that is measured is the experimental unit. In this study, we are measuring

new software development projects. b. The population would be the set of all new software development projects. The 24

projects that were examined were selected from this population. c. Based on the sample of 24 projects tested, we believe that the success rate for all new

software development projects would be somewhere around the value 62.5% (15/24). 1.4 a. The object that is measured is the experimental unit. In this study, we are measuring

earthquakes that occurred around the world between 1940 and 1995. b. Since there were many more than 15 earthquakes around the world between 1940 and

1995, the 15 earthquakes that were measured represent a subset from the populations. Therefore, they are a sample.

1.6 a. The populations are the total water flow amounts required to effectively cool all the

batches of Florida vegetables under the two methods. The samples are the total water flow amounts recorded for the 20 batches of green tomatoes sampled. The type of statistical inference to be made is most likely a comparison of total water flow amounts for the two methods.

b. Since the sample data comes from both cooling methods, comparing the average water

flow amounts from the two methods would be an effective comparison of the two systems.

1.8 The population is the defective status of all items coming off an assembly line. The sample is

the defective status of the items examined by the quality control engineer. The inference of interest is to estimate the percentage of all items that are defective.

1.10 a. Flight capability can have only 2 possible outcomes: volant or flightless. Thus, it is qualitative. b. Habitat type can have only 3 possible outcomes: aquatic, ground terrestrial, or aerial

terrestrial. Thus, it is qualitative. c. Nesting site can have only 4 possible outcomes: ground, cavity within ground, tree, or cavity above ground. Thus, it is qualitative. d. Nest density can have only 2 possible outcomes: high or low. Thus, it is qualitative. e. Diet can have only 4 possible outcomes: fish, vertebrates, vegetables, or invertebrates. Thus, it is qualitative.

2 Chapter 1

f. Body mass is measured in grams, a meaningful number. Thus, it is quantitative. g. Egg length is measured in millimeters. Therefore, it is a quantitative variable. h. Extinct status can have only 3 possible outcomes: extinct, absent from island, or

present. Thus, it is qualitative. 1.12 a. The object that is measured is the experimental unit. In this study, we are measuring

smokers. b. The two variables that are being measured for each smoker are the type of screening

method used and the age at which a tumor is first detected. c. Type of screening method used is either CT or chest X-ray. Therefore it is a qualitative

variable. Age at which a tumor is first detected will be measured on a numerical scale.

Therefore it is a quantitative variable. 1.14 a. Length of maximum span can take on values such as 15 feet, 50 feet, 75 feet, etc.

Therefore, it is quantitative. b. The number of vehicle lanes can take on values such as 2, 4, etc. Therefore, it is

quantitative. c. The answer to this item is "yes" or "no," which are not numeric. Therefore, it is

qualitative. d. Average daily traffic could take on values such as 150 vehicles, 3,579 vehicles, 53,295

vehicles, etc. Therefore, it is quantitative. e. Condition can take on values "good," "fair," or "poor," which are not numeric.

Therefore, it is qualitative. f. The length of the bypass or detour could take on values such as 1 mile, 4 miles, etc.

Therefore, it is quantitative. g. Route type can take on values "interstate," U.S.," "state," "county," or "city," which are

not numeric. Therefore, it is qualitative. 1.16 a. The population of interest is the direction of travel of all sea turtle hatchlngs from a

dark beach. b. The sample is the 180 directions collected from the sea turtles on the three nights in the

study. c. The direction of travel is a qualitative variable as the responses fall into categories. (E,

W, NW, etc.)

Introduction 3

1.18 Location is a qualitative variable since the responses would fall into one of several categories (NW, SE, etc.).

PCP level is a quantitative variable as the responses represent the amount (.02, 004, etc.) of

PCB present. 1.20 Quantitative data are those that represent the quantity or amount of something. Qualitative

data are those that can be classified into one of several categories. a. quantitative b. qualitative c. qualitative d. quantitative e. quantitative f. quantitative g. qualitative h. quantitative