Chapter 1 Exploring Data

Question 1

individuals

Answer 1

objects described in a set of data, can be people, animals, things, etc

Question 2

variable

Answer 2

any characteristic of an individual, they can take different values for different individuals

Question 3

categorical variable

Answer 3

places an individual into one of several groups of categories

Question 4

quantitative variable

Answer 4

takes numerical values for which it makes sense to find an average

Question 5

distribution

Answer 5

tells us what values the variable takes and how often it takes these values

Question 6

pie charts and bar graphs

Answer 6

can be used to display the distribution of a categorical variable more clearly

Question 7

marginal distribution of one of the categorical variables in two way table

Answer 7

distribution of the values of that variable among all individuals described in the table

Question 8

conditional distribution of a variable

Answer 8

describes the values of that variable among individuals who have specific value of an other variable

Question 9

association

Answer 9

occurs in two variables if specific values of one variable tend to occur in common with specific values of the other

Question 10

Simpson’s paradox

Answer 10

an association between two variables that holds for each individual value of a third variable can be changed or reversed when the data for all values of the third variable are combined

Question 11

roughly symmetric: within a distribution

Answer 11

if the right & left sides of the graph are approximately mirror images of each other

Question 12

skewed to the right: within a distribution

Answer 12

if the right side of the graph (containing half of the observations with larger values) is much longer than the left side.

Question 13

skewed to the left: within a distribution

Answer 13

if the left side of the graph is much longer than the right side

Question 14

median M

Answer 14

midpoint of the distribution, the number that half the observations are smaller and the other half are larger

Question 15

steps for find the median (M)

Answer 15

1. arrange all observations in order of size, from smallest to largest. 2. if the number of observations n is off, the median M is the center observation in the ordered list. 3. if the number of observations n is even, the median M is the average of the two center observations in the ordered list

Question 16

the 1.5 X IQR rule for outliers

Answer 16

an observation can be considered an outlier if it falls either more than 1.5 X IQR above the third quartile or 1.5 X IQR below the first quartile

Question 17

standard deviation

Answer 17

measures the average distance of the observations to the mean

Question 18

how to calculate the standard deviation

Answer 18

find the average of the squared distances and then taking the squared root

Question 19

variance

Answer 19

average squared distance to the mean