STAT_Ch 7. Sampling

Which of the following is equivalent to the mean?

Average

What is the name for the line that goes through the mean of a normal distribution curve?

Central line

Which of the following conditions must be met for a sample to be a stratified random sample?

It must include all members of a population.

Which theorem states that the larger the sample size, the closer the sample mean will be to the mean of the population?

Law of large numbers.

What is a sequence of equally distributed variables?

Random sample

Jackie is conducting a survey. Her population contains 100 people with strata divided into the following proportions: 20%, 10%, 10%, 30%, 30% If Jackie wants to select 10 people for her sample, then how many people from each stratum would she pick?

She would randomly select 2, 1, 1, 3, and 3 individual(s) from each stratum respectively.

What is a type of random sampling where the variables have an equal, and unsystematic, chance of selection?

Simple random sampling

Which of the following statements best describes the central limit theorem?

The more you run a random experiment, the more its results will follow a normal distribution.

For which type of study is it most appropriate to use a random sample?

To gather information about a large population.

You should use cluster sampling when the clusters are _____ in a population.

natural

Why is systematic random sampling unbiased?

Because the system selects the sample rather than an individual

Which of the following is a type of random sampling?

Cluster sampling

When selecting strata groups, it is recommended you have:

No more than 4 to 6 strata.

A(n) _____ is all members of a specified group.

Population

What is the name for all the members of a specified group?

Population

A _____ is a part of a population used to describe the whole group.

Sample

What is a part of a population used to describe the whole group?

Sample

To use systematic random sampling, you must first create a list of your population, and then:

Select a beginning number

If you divide the standard deviation of the sample set by the square root of the sample size, then what do you find?

Standard error

Which type of random sampling divides members of a population into homogeneous subgroups?

Stratified random sampling

How do cluster sampling and stratified random sampling differ?

Stratified random sampling requires selection from each group proportional to their share of the population, but cluster sampling does not.

What is the method that requires selecting samples based on a system of intervals in a numbered population?

Systematic random sampling

If a data set has a large standard error, then what does that imply about the data set?

That the data set represents a broad range of numbers

Which of the following is an implication of the central limit theorem?

The mean of the population can be approximated by the mean of the sample means.

Stratified random sampling works best when the researcher is familiar with the demographics of the population and:

The proportion of the demographics are important to the data being collected.

A researcher is studying a population, and decides to use simple random sampling. Why might they have made this decision?

The researcher doesn't know a lot about the population.

Which of the following statements is an implication of the central limit theorem?

The standard deviation of the population can be approximated by the standard deviation of the sample means divided by the square root of the sample size.

A biologist has a sample of lizards from a certain area, and their weights are normally distributed. If the biologist wants to expand the sample, but maintain its integrity, what should they do? Why?

They should randomly choose lizards from the same area, because the data set only maintains its integrity if the new members of the sample come from a random sampling.

Assuming that the population is not normally distributed to begin with, what will happen to the sample means with a large enough sample size?

They will be normally distributed.

When members belong to multiple groups in the population this is called _____. Cluster sampling _____ have this.

crossover; cannot

What is a Z-score?

The measure of distance from the mean in terms of numbers of standard deviation

A statistician calculates the probability of an event in an experiment. After a dozen trials of the experiment, the statistician finds that the theoretical probability and the experimental probability differ. What is the likely reason for this?

The statistician hasn't completed enough trials of the experiment.

Which of the following is TRUE, according to the central limit theorem?

The variance of the population can be approximated by the variance of the sample means divided by the sample size.

A scientist is measuring the diameters of tree trunks, measuring twenty trees per trip. If the scientist increases their sample size to thirty per trip, then what change should they expect to see in the means of the samples?

They will become more normally distributed.

Which is a sampling method that involves separating the population into clusters, and then selecting random samples from each of the clusters?

Two-way cluster sampling.

When doing systematic sampling, you must remember that all outcomes must be given _____ chance of being selected.

equal

How do you find the mean of a data set?

Add up all the values in the data set, then divide by the total number of values in the data set.

Simple random sampling is usually done _____.

without replacement

What does the normal distribution look like?

A bell

What is the standard error?

A measure of the accuracy of the mean

The law of large numbers shows a relationship between the theoretical probability and the _____.

experimental probability

According to the law of large numbers, the difference between the theoretical probability and the experimental probability becomes _____ as more experiments are performed, or as the sample size gets larger.

smaller

_____ is a sampling method where different groups within a population are used as a sample.

Cluster sampling

To find the interval you need, take your population size and divide by the _____.

sample size

The law of large numbers is also known as:

Bernoulli's law.