Statistics Chapter 1 & 2

An editorial criticized a chart captio that described a dental rinse as one that "reduces the Chan e of plaque on teeth by over 350%" what is wrong with this statement.

A reduction of 100% would eliminate all plaque, so it is not possible to reduce it by more than 100%

What is a voluntary response sample?

A sample in which the subjects themselves decide whether to be included in the study.

Ratio Data

Differences between measurements, true zero exists. Ex. Height, Age, Weekly, Food Spending

Interval Data

Differences between values can be found, but there is no absolute 0. (Temp. and Time standardized exam score)

Number of days of rainfall in a year is 15

Discrete

Eighty patients with stomach cancer are divided into 2 groups, one group receives an experimental drug to fight cancer, the other a placebo. after one year, the spread of the cancer is measured

Experiment

An ad for airbags claimed the proper usage of airbags "reduces the chance of fatality in a car crash by 350%. What is wrong with this statement?

If airbags eliminated all fatalities, it would result in a 100% reduction, so it is not possible to reduce fatalities by more than 100%

In a survey of 686 subjects, each was asked how often he or she read a book. The survey subjects were internet users who responded to a question that was posted on a news website

It is flawed because it is a voluntary response sample

In a survey of 653 subjects, each was asked how often he or she played sports. This survey subjects were internet users who responded to a question that was on a news website.

It is flawed because it is a voluntary sample

When a can is randomly selected, it is found to have a length of 17.05 ft

It is from a continuous data set because the number of possible values is infinite and. It countable

When a limo is ramdomly selected, it is found to have a tire pressure of 30 psi

It is from a continuous date set because the number of possible values is infinite and not countable

A women is selected by a marketing company to participate in a paid focus group. The group says that the woman was selected because she was randomly chosen from all adults

Random sampling

A man is selected by a marketing company to participate in a paid focus group. the company says that the man was selected because he was randomly chosen from all men in his tax bracket

Stratified sampling

A man is selected by a marketing company to participate in a paid focus group. The company says that the man was selected because every 20,000th person in the phone number listings was being selected.

Systematic sampling

In a survey, the eye colors of respondents are identified as 0 for brown eyes, 2 for green eyes, and 3 for anything else. The average (mean) is calculated for 673 respondents and the result is 1.1.

The data are at the nominal level of measurement. Such data are not counts or measures of anything, so it makes no sense to compute their average (mean).

Brands of toothpaste

The nominal level of measurement is most appropriate because the data cannot be ordered

Volume of planets in cubic meters

The ratio level of measurement is most appropriate because the data can be ordered, differences (obtained by subtraction) can be found and are meaningful and there is a natural starting zero point

Determine which of the four levels of measurement is most appropriate for the data below. Length of the side of a square in cm

The ration level of measurement is most appropriate because the data can be ordered, differences (obtained by subtraction) can be found and are meaningful and there is a natural starting zero point.

The mean IQ score for college students is 105

The value is a parameter because it is a numerical measurement describing some characteristic of a population

A survey found that 7% of all respondents have jobs

The value is a statistic because it is a numerical measurement describing some characteristic of a sample

A survey found that 26% of all respondents go to school

The value is a statistical because it is a numerical measurement describing some characteristic of a sample

In a study of a gender selection method used to increase the likelihood of a baby being born a girl, 2033 users of the method gave birth to 995 boys and 1038 girls. there is about an 18% chance of getting that many girls if the method had no affect.

because there is an 18% chance of getting that many girls by chance, the method DOES NOT HAVE STATISTICAL SIGNIFICANCE. NOT MANY couples would likely use a procedure that raises the likelihood of a girl from the approximate 50% rate expected by chance to the 51% produced by this method. So this method DOES NOT HAVE PRACTICAL SIGNIFICANCE.

Nominal Data

data of categories only. Data cannot be arranged in an ordering scheme. (Gender, Race, Religion, maritial status, type of car owned)

Determine whether the value is from a discrete or continuous data set. Number of pieces of lumber used to make a deck is 113

discrete

Volume of liquid in a glass 350 mL

discrete

based on a study of weights of men and women who watch TV, a researcher concludes that watching television causes people to gain weight? do you agree with this conclusion?

no, there may be a relationship between watching television and weight gain, but that does not mean that one causes the other

based on a study of heights of men and women who play basketball, a researcher concludes that the exercise from playing basketball causes people to grow taller. do you agree with this conclusion?

no. there may be a relationship between height and playing basketball, but that does not mean that one causes the other

Research is conducted to determine if there is a relationship between brain cancer and use of cell phones

observational study

ordinal data

ordered categories, Ex. service quality rating, student letter grades.

class width

subtracting a lower class limit from the next consecutive lower class limit

In a survey, the favorite sports of respondents are identified as 10 for basketball, 30 for baseball, and 40 for anything else. The average (mean) is calculated for 782 respondents and the result is 22.3

the data are at the NOMINAL level of measurement. Such data are not counts or measures of anything, so it makes no sense to compute their average (mean)

length of the side of a square in cm

the ratio level of measurement is most appropriate because the data can be ordered, differences (obtained by subtraction) can be found and are meaningful, and there is natural starting point