OpenStax - Ch. 2 Descriptive Statistics

Question 1

Box plot

Answer 1

a graph that gives a quick picture of the middle 50% of the data.

Question 2

First Quartile

Answer 2

the value that is the median of the lower half of the ordered data set.

Question 3

Frequency

Answer 3

the number of times a value of the data occurs.

Question 4

Frequency Polygon

Answer 4

looks like a line graph but uses intervals to display ranges of large amounts of data.

Question 5

Frequency Table

Answer 5

a data representation in which grouped data is displayed along with the corresponding frequencies.

Question 6

Histogram

Answer 6

a graphical representation in x-y form of the distribution of data in a data set; x represents the data and y represents the frequency, or relative frequency. The graph consists of contiguous rectangles.

Question 7

Interquartile Range

Answer 7

or IQR, is the range of the middle 50 percent of the data values; the IQR is found by subtracting the first quartile from the third quartile.

Question 8

Interval

Answer 8

also called a class interval; an interval represents a range of data and is used when displaying large data sets.

Question 9

Mean

Answer 9

a number that measures the central tendency of the data; a common name for mean is ‘average.’

Question 10

Median

Answer 10

a number that separates ordered data into halves; half the values are the same number or smaller than the median and half the values are the same number or larger than the median. The median may or may not be part of the data.

Question 11

Midpoint

Answer 11

the mean of an interval in a frequency table.

Question 12

Mode

Answer 12

the value that appears most frequently in a set of data.

Question 13

Outlier

Answer 13

an observation that does not fit the rest of the data.

Question 14

Paired Data Set

Answer 14

two data sets that have a one to one relationship so that: both data sets are the same size, and each data point in one data set is matched with exactly one point from the other set.

Question 15

Percentile

Answer 15

a number that divides ordered data into hundredths; percentiles may or may not be part of the data. The median of the data is the second quartile and the 50th percentile. The first and third quartiles are the 25th and the 75th percentiles, respectively.

Question 16

Quartiles

Answer 16

the numbers that separate the data into quarters; quartiles may or may not be part of the data. The second quartile is the median of the data.

Question 17

Relative Frequency

Answer 17

the ratio of the number of times a value of the data occurs in the set of all outcomes to the number of all outcomes.

Question 18

Skewed

Answer 18

used to describe data that is not symmetrical;

when the right side of a graph looks “chopped off” compared the left side, we say it is “skewed to the left.”

When the left side of the graph looks “chopped off” compared to the right side, we say the data is “skewed to the right.”

Alternatively: when the lower values of the data are more spread out, we say the data are skewed to the left.

When the greater values are more spread out, the data are skewed to the right.

Question 19

Standard Deviation​

Answer 19

a number that is equal to the square root of the variance and measures how far data values are from their mean; notation: s for sample standard deviation and σ for population standard deviation.

Question 20

Variance

Answer 20

mean of the squared deviations from the mean, or the square of the standard deviation;

for a set of data, a deviation can be represented as x – x¯x¯ where x is a value of the data and x¯x¯ is the sample mean.

The sample variance is equal to the sum of the squares of the deviations divided by the difference of the sample size and one.