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What is statistics?
the science of planning studies and experiments, obtaining sample data, and then organizing, summarizing, analyzing, interpreting data, and drawing conclusions about a population based on the data
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What is sample data?
the collection of observations (such as measurements, genders, survey responses---data values)
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What is a population?
- the complete collection of all individuals (scores, people, measurements, and so
- on) to be studied; the collection is complete in the sense that it includes all of the individuals to be studied
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What is a parameter?
a numerical measurement describing some characteristic of a population.
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What is a statistic?
a numerical measurement describing some characteristic of sample data
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What is categorical data?
Qualitative! also called attribute; consists of names or labels
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What is a nominal level of measurement?
data that consists only of names, labels, or categories. Cannot be listed in quantitative schemes, such as low to high.
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What is an example of measurements that are nominal?
Survey responses (yes, no, undecided)
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What is an ordinal level of measurement?
data that can be arranged in a degree of order, but differences between data values cannot be determined or are meaningless. No actual values are attributed.
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What's an example of an ordinal level of measurement?
Grades: A, B, C... (but not saying what distinguishes an A from a B, etc)
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What is discrete data?
data when the number of possible values is a finite (countable) number
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What is an example of discrete data?
the number of eggs that a hen lays
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What is continuous data?
data that results from infinitely many possible values that correspond to some continuous scale that covers a range of values without gaps.
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What does a frequency distribution do?
shows how a data set if partitioned among all of several categories by listing all of the categories along with the number of data values in each of the categories
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What is a histogram?
a graph consisting of bars of equal width drawn adjacent to each other (without gaps)
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What are the properties of standard deviation?
- measures variation among data values
- has the same units of measurement as the original data
- A value is typically unusual if it differs from the mean by more than two standard deviations
- Only compare standard deviation of two different data sets if they have means that are approximately the same.
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What is the formula for standard deviation?
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What is the coefficient of variation?
describes the standard deviation, relative to the mean
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What is the formula for the coefficient of variation?
cv (coefficient value) = sd/mean *100%
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What are quartiles?
measures of location that divide a set into four groups. There are three quartiles, so think of them as the lines between divisions
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What is a 5-number summary?
the three quartiles with a minimum and maximum value added on
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What is an interquartile range?
a measure of the difference between two quartiles (not necessarily consecutive)
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What is a boxplot?
- a box-and-whisker-diagram; a graph of a data set, consisting of a line extending from the minimum value to the maximum value, and a box with lines drawn at the first quartile, Q1; the median; and the third quartile, Q3.
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What makes a modified boxplot modified from a normal one?
- a special symbol is used to identify asterisk
- the solid horizontal line extends as far as the minimum and maximum data values that are NOT outlies
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How many values fall within one standard deviation of the mean?
68%
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How many values fall within 2 standard deviations of the mean?
95%
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How many values fall within 3 standard deviations of the mean?
99.7%
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