Section 1.1 Introduction to the Practice of Statistics
ΒΆDefinition 1.1.1. statistics.
how to collect, organize, summarize and analyze information so that conclusions can be drawn with a measure of confidence.
Definition 1.1.2. descriptive stats.
entails organizing and summarizing collected data.
Definition 1.1.3. inferential stats.
methods for taking sample results and extending it to the population with some measure of reliability.
Definition 1.1.4. population.
entire group of interest in a study
Definition 1.1.5. individual.
a single person or object being studied
Definition 1.1.6. sample.
subset of the population being studied
Definition 1.1.7. statistic.
numerical summary of a sample
Definition 1.1.8. parameter.
numerical summary of a population
Definition 1.1.9. variables.
characteristics of individuals in the population
Definition 1.1.10. qualitative variable.
responses based on attributes or characteristics
Definition 1.1.11. quantitative variable.
responses are numerical measures, with a natural ordering i.e. it makes sense to compare via < or >
Definition 1.1.12. discrete variable.
finite or countable number of possible values e.g. number of children
Definition 1.1.13. continuous variable.
infinite number of possible values e.g. height
Exercises Statistic or Parameter?
For each description which follows, determine whether the numerical quantity is a statistic or parameter.
1.
In a study of all 2223 passengers aboard the Titanic, it is found that 706 survived when it sank.
parameter
2.
A recent survey of a sample of MBA's reported that the average salary for an MBA is more than $82,000. (Source: The Wall Street Journal)
statistic
3.
Starting salaries for all of the 667 MBA graduates from the University of Chicago Graduate School of Business increased 8.5% from the previous year.
parameter
4.
In a recent poll of Salt Lake Community College students, 83% of students owned a vehicle.
statistic
5.
In a recent survey of 457 attendees of Jumanji, 402 would recommend the movie to a friend.
parameter, unless you consider the population to be all people who have seen Jumanji
Exercises Discrete or Continuous Variable?
1.
In a survey of 1059 adults, it is found that 39% of them have guns in their homes
discrete
2.
The number of heads obtained after flipping a coin five times
discrete
3.
The distance Tiger Woods can drive a golf ball
continuous
4.
oints scored in a basketball game
discrete
5.
Volume of water lost each day from a leaky faucet
continuous
6.
Length of a song
continuous, but could be discrete if measured in seconds
7.
Number of words in a song
discrete
Reading Questions Qualitative or Quantitative Variable?
1.
Gender
qualitative
2.
Temperature
quantitative
3.
Nation of origin
qualitative
4.
Number of siblings
quantitative
5.
Number of days
quantitative
6.
Grams of carbohydrates in a donut
quantitative
7.
Phone number
qualitative
8.
Value of a house
quantitative
9.
Zip code
qualitative
Reading Questions 2011 BMW Models
The following information relates to the 2011 model year product line of BMW automobiles. Identify the individuals in the study, the variables and if the data corresponding to the variables are qualitative or quantitative, and continuous or discrete.
| Model | Body Style | Weight | Number of Seats |
| 3 Series | Coupe | 3362 | 4 |
| 5 Series | Sedan | 4056 | 5 |
| 6 Series | Convertible | 4277 | 4 |
| 7 Series | Sedan | 4564 | 5 |
| X3 | Sport Utility | 4012 | 5 |
| Z4 | Coupe | 3505 | 2 |
1.
Individuals: Answer2.
Variable(s): Answer| Variable | Qual./Quant. | Disc./Cont. |
| body style | qualitative | N/A |
| weight | quantitative | continuous |
| number of seats | quantitative | discrete |
Reading Questions Smoker's IQ
A study was conducted in which 20,211 18--year old recruits were given an exam to measure IQ. In addition, the recruits were asked to disclose their smoking status. An individual was considered a smoker if he smoked at least 1 cigarette per day. The goal of the study was to determine whether adolescents aged 18 to 21 who smoke have a lower IQ than nonsmokers. It was found that the average IQ of the smokers was 94, while the average IQ of nonsmokers was 101. The researchers concluded that lower IQ individuals are more likely to chose to smoke, not that smoking makes people less intelligent.