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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
What is sample data?
the collection of observations (such as measurements, genders, survey responses---data values)
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
What is a parameter?
a numerical measurement describing some characteristic of a population.
What is a statistic?
a numerical measurement describing some characteristic of sample data
What is categorical data?
Qualitative! also called attribute; consists of names or labels
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.
What is an example of measurements that are nominal?
Survey responses (yes, no, undecided)
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.
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)
What is discrete data?
data when the number of possible values is a finite (countable) number
What is an example of discrete data?
the number of eggs that a hen lays
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.
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
What is a histogram?
a graph consisting of bars of equal width drawn adjacent to each other (without gaps)
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.
What is the formula for standard deviation?
What is the coefficient of variation?
describes the standard deviation, relative to the mean
What is the formula for the coefficient of variation?
cv (coefficient value) = sd/mean *100%
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
What is a 5-number summary?
the three quartiles with a minimum and maximum value added on
What is an interquartile range?
a measure of the difference between two quartiles (not necessarily consecutive)
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.
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
How many values fall within one standard deviation of the mean?
How many values fall within 2 standard deviations of the mean?
How many values fall within 3 standard deviations of the mean?
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