Ch 2 Descriptive Statistics

Question 1

ordered array

Answer 1

data arranged from smallest to largest (usually)

Question 2

relative frequencies

Answer 2

the proportion of values falling into a class interval. We divide the number of values in each category by the total number of values

Question 3

experimental probability or empirical proability

Answer 3

interpreting the relative frequencies as the probablity of occurence within a given interval

Question 4

frequency histogram and frequency polygon

Answer 4

special types of bar and line graphs

Question 5

cut points

Answer 5

points on the horizontal axis where the bars meet

Question 6

stem and leaf displays

Answer 6

bears a strong resemblance to the histogram and served the same purpose

Question 7

statistic

Answer 7

descriptive measure computed from a sample

Question 8

parameter

Answer 8

descriptive measure computed from population

Question 9

measures of central tendency

Answer 9

mean, median and mode

Question 10

(arithmetic mean)

Answer 10

average

Question 11

first property of a mean

Answer 11

uniqueness, for a given set of data, there is exactly one arithmetic mean

Question 12

second property of a mean

Answer 12

simplicity, the arithmetic mean is easily understood easy to compute

Question 13

third property of a mean

Answer 13

since each and every value in a set of data enters into the computation of the mean and, in some cases, can so distort it that it becomes undesirable as a measure of central tendency

Question 14

outliers(extreme values)

Answer 14

values that deviate appreciably from most of the measurements in a data set

Question 15

robust estimators

Answer 15

estimators that are insensitive to outliers

Question 16

trimmed mean

Answer 16

a robust estimator of central tendency

Question 17

median

Answer 17

value that divides the ordered array into 2 equal parts

Question 18

first property of the median

Answer 18

uniqueness, as with mean, there is a unique median for a given set of data

Question 19

second property of the median

Answer 19

simplicity, the median is easy to calculate

Question 20

third property of the median

Answer 20

robustness, it’s not as drastically affected by extreme values like the mean

Question 21

mode

Answer 21

the value that occurs most frequently, if all the data items are different, there is no mode

Question 22

skewness

Answer 22

classification of data distributions on the basis of whether they are symmetric or asymetric

Question 23

symmetric

Answer 23

the left half of its graph (histogram or frequncy polygon) will be a mirror image of its right half

Question 24

skewed distribution

Answer 24

if the graph of a distribution is asymmetric

Question 25

skewed to the right, positively skewed

Answer 25

graph has long tail to the right

Question 26

skewed to the left, negatively skewed

Answer 26

graph has long tail to left

Question 27

measures of dispersion

Answer 27

describe the variation, spread and scatter of the distribution

Question 28

range

Answer 28

difference between the largest and smallest values in a set of observations

Question 29

variance

Answer 29

measures dispersion based on how the data points are scattered about the mean

Question 30

standard deviation (SD)

Answer 30

square root of the variance, has the same units of the data

Question 31

coefficient of variation

Answer 31

used for comparing the variation of 2 or more distributions

Question 32

five number summary

Answer 32

given a set of n observations x1, x2,….xn, the pth percentile P is the value of X such that p percent or less of the observations are greater than P

Question 33

interquartile range (IQR)

Answer 33

difference between the third and first quartiles

Question 34

box and whisker plots (boxplots)

Answer 34

graphical representation of the five number summary

Question 35

kurtosis

Answer 35

measure of the degree to which a distribution is “peaked” or flat in comparison to a normal distribution whose graph is characterized by a bell shaped distribution