A histogram displays quantitative data with touching bars whose heights show how many values fall in each interval.
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histogram
A histogram groups quantitative data into intervals and draws adjacent bars, so the shape of the distribution is easy to see.
Category: Graphing Data
Question 2
The median is the middle value of a data set after the values are put in order.
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median
The median splits ordered data in half. When the number of values is even, it is the average of the two middle values.
Category: Measures of Center
Question 3
The mode is the value that occurs most often in a data set.
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mode
The mode is the most frequent value, and it is the only measure of center that also works for qualitative data.
Category: Measures of Center
Question 4
The range of a data set equals its largest value minus its smallest value.
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range
The range is the simplest measure of spread, but because it uses only the two extreme values, an outlier can change it greatly.
Category: Measures of Spread
Question 5
The variance is found from the squared deviations from the mean (for a sample, their sum divided by n - 1), and its square root gives the standard deviation.
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variance
The variance measures spread in squared units. For a sample, the squared deviations are summed and divided by n - 1, and taking the square root returns the spread to the original units as the standard deviation.
Category: Measures of Spread
Question 6
An outlier is an observation that lies unusually far from the rest of the data.
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outlier
An outlier stands apart from the other values. It may be an error or a real but unusual observation, so it should be investigated.
Category: Measures of Location
Question 7
When the left half of a distribution is a mirror image of its right half, the distribution shows symmetry.
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symmetry
Symmetry means the shape is the same on both sides of the center. In a distribution with symmetry, the mean and median are about equal.
Category: Skewness
Question 8
A distribution with a long tail stretching toward higher values is skewed to the right.
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skewed
A skewed distribution has one tail longer than the other. A long right tail is called a right or positive skew.
Category: Skewness
Question 9
A bimodal distribution has two distinct peaks.
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bimodal
A bimodal distribution has two high points, which can happen when the data mix two different groups.
Category: Skewness
Question 10
The quartiles split ordered data into four parts, each holding about a quarter of the values.
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quartiles
The three quartiles, Q1, Q2 (the median) and Q3, divide ordered data into four groups of about equal size.
Category: Measures of Location
Question 11
The 90th percentile of a data set is the value at or below which about 90% of the values fall.
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percentile
A percentile describes a value's position by the percentage of data at or below it, so low percentiles go with low data values.
Category: Measures of Location
Question 12
In a box plot, the lines that extend outward from each end of the box are called whiskers.
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whiskers
The whiskers reach from the box toward the smallest and largest values, showing how far the data extend beyond the quartiles.
Category: Measures of Location
Question 13
In a stem plot, each leaf shows the last digit of a data value, and the stem shows the digits in front of it.
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leaf
In a stem plot, the leaf is the final digit of a value, written beside its stem so every individual data value stays visible.
Category: Graphing Data
Question 14
About 68% of the values in a bell-shaped distribution lie within 1 standard deviation of the mean.
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1
The empirical rule says about 68% of bell-shaped data lie within 1 standard deviation of the mean and about 95% lie within 2.
Category: Z-Scores and Empirical Rule
Question 15
When every value in a data set is identical, the standard deviation equals 0.
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0
If all values are the same, every deviation from the mean is 0, so the standard deviation is 0. It can never be negative.
Category: Measures of Spread