Researchers collect data from a sample, a subset selected from the larger group they want to learn about.
Missing Word
sample
A sample is the part of the population from which data are actually gathered, and its results are used to learn about the whole group.
Category: Key Terms
Question 2
A parameter is a numerical characteristic of an entire population, such as the true mean income of every household in a state.
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parameter
A parameter describes a whole population. It is usually unknown and is estimated from sample data.
Category: Key Terms
Question 3
A statistic is a number computed from the data of a selected subset, such as the mean height of 50 surveyed adults.
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statistic
A statistic describes a sample and is used to estimate the matching population parameter.
Category: Key Terms
Question 4
Qualitative data, also called categorical data, describe attributes such as hair color or eye color.
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Qualitative
Qualitative data place individuals into categories rather than recording numerical amounts.
Category: Data and Measurement
Question 5
Quantitative data that take only separate, countable values, such as the number of pets in a home, are discrete.
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discrete
Discrete data come from counting, so only certain values such as 0, 1 or 2 are possible.
Category: Data and Measurement
Question 6
Quantitative data obtained by measuring, such as the time it takes to run a mile, are continuous.
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continuous
Continuous data come from measuring and can take any value in a range, including fractions and decimals.
Category: Data and Measurement
Question 7
Convenience sampling chooses people simply because they are easy to reach, such as shoppers walking past a store entrance.
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Convenience
Convenience sampling uses whoever is readily available. Because no random selection is involved, it often produces biased results.
Category: Sampling Methods
Question 8
When sampling with replacement, a chosen member is put back and may be picked again.
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replacement
Sampling with replacement returns each selected member to the population, so the same member can be selected more than once.
Category: Sampling Methods
Question 9
A census gathers information from every single member of a population.
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census
A census measures the entire population instead of a part of it. It is often too costly or slow, which is why researchers usually sample.
Category: Sampling Methods
Question 10
The nominal level of measurement applies to unordered categories such as favorite color or smartphone brand.
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nominal
Nominal is the lowest level of measurement. Its categories are names only, with no order and no meaningful arithmetic.
Category: Data and Measurement
Question 11
At the ratio level of measurement, zero means none of the quantity is present, so a 10-kilogram bag weighs twice as much as a 5-kilogram bag.
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ratio
The ratio level has all the properties of the interval level plus a true zero, which makes comparisons such as twice as much meaningful.
Category: Data and Measurement
Question 12
The frequency of a data value is the number of times that value occurs in a data set.
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frequency
Frequency is a simple count of how often a value appears. Dividing it by the total gives the relative frequency.
Category: Frequency Tables
Question 13
A placebo is an inactive pill, such as a sugar pill, made to look exactly like the real drug being tested.
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placebo
A placebo looks like the active treatment but cannot directly affect the response. Giving it to the control group lets researchers separate the effect of the drug from the effect of simply being treated.
Category: Experimental Design
Question 14
A variable, usually written with a capital letter such as X, is a characteristic of interest that can take different values from one member of a population to the next.
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variable
A variable is the characteristic being studied, such as commute time or major. Its recorded values for the individuals are the data.
Category: Key Terms
Question 15
Probability is the branch of mathematics that measures how likely an outcome is on a scale from 0 to 1.
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Probability
Probability describes the long-run chance of an outcome, from 0 (impossible) to 1 (certain). It is the tool statistics uses to judge how much sample results can vary by chance.
Category: Key Terms