Statistics: Quiz 1

symmetry

bell shaped triangular uniform or rect.

Data from a sample of citizens of a certain country yielded the following estimates of average TV viewing time per month for all the citizens. The times are in hours and minutes.​ Is the study descriptive or​ inferential?

​Inferential, because the statistics are used to make an inference about the population

Is the following study descriptive or​ inferential? In a statistical​ magazine, average professional​ athletes' salaries in three sports were compiled and compared for the years 1993 and 2003.

Descriptive, because the statistics are a summary of the average salaries of professional athletes in three sports

a. Frequency and relative frequency b. Percentage and relative frequency

Frequency is the number of times a particular distinct value occurs. Relative frequency is the ratio of the frequency of a value to the total number of observations. A relative frequency is the same as a percentage expressed as a decimal.

What is a frequency distribution of qualitative data and why is it​ useful?

It is a listing of the distinct values and their frequencies. It is useful because it provides a table of the values of the observations and how often they occur.

A nationwide survey of 1000 adults found that 50​% of respondents favored a plan to break up the 12​ megabanks, which then controlled about 69​% of the banking industry. Complete parts​ (a) and​ (b) below. Identify the population and sample for this study. Choose the correct answer below.

The population is all adults in the country. The sample is the 1000 adults surveyed. The percentage is a descriptive​ statistic, since it summarizes information about how much of the sample favors breaking up the megabanks.

In​ sampling, explain why obtaining a representative sample is important. Why is obtaining a representative sample​ important?

The sample must be representative in order to use inferential statistics to draw conclusions about the entire population.

A study is conducted to determine if there is a relationship between height and childhood exposure to measles.Students have their height measured and are asked about childhood exposure to measles. Does the description correspond to an observational study or an​ experiment?

The study is an observational because the study examines individuals in a sample, but does not try to influence the response variable.

A recent article postulated that support for a certain​ scientist's theories increases with level of education. The table shown to the right provides percentages of a certain​ country's adults, by educational​ level, who believe that evolution is a scientific theory well supported by evidence. Complete parts a and b. Education Percentage Postgraduate education ​65% College graduate ​52% Some college education ​32% High school or less ​20% Bold a. a. Do you think that this study is descriptive or​ inferential? Explain your answer. ​If, in​ fact, the study is​ inferential, identify the sample and population.

The study is inferential because a sample was used to make an inference about the population. ​If, in​ fact, the study is​ inferential, identify the sample and population. A. The sample is the adults who were interviewed. The population is the​ country's adult population.

A report stated that ​"65​% of people between the ages of 40 and 54 favor tax cuts.​" The percentage of 65​% was computed from sample data. Complete parts​ (a) through​ (d) below. a. Identify the population under consideration. b. Identify the sample under consideration. c. Is the statement in quotes descriptive or​ inferential d. If you wanted to make it clear that the percentage of 65​% was computed from sample​ data, how would you rephrase the statement in​ quotes?

a. population is all people between the ages of 40 and 54. b. sample is all people between the ages of 40 and 54 who were surveyed. c. The statement is​ inferential, since it draws a conclusion about the population based on a sample. d. 65​% of those surveyed between the ages of 40 and 54 favor tax cuts.cuts.​"

A poll is conducted in which 253253 women are asked about what type of car they drive. Is the study an observational study or a designed​ experiment?

observational

In a designed​ experiment...

researchers impose treatments and controls and then observe characteristics and take measurements.

In an observational​ study...

researchers simply observe characteristics and take​ measurements, as in a sample survey

Modality

unimodal= 1 peak bimodal= 2 peaks multimodal= 3 or more peaks