5, MOVE UP SEVEN UNITS AND TO THE RIGHT FIVEUNITS. ANOTHER POINT ON TH...
5
, move up seven units and to the right fiveunits. Another point on the line, thus, is (13,16).I
MPORTANT
I
NFORMATION ABOUT
S
LOPE
The following are a few rules about slope that you should keep in mind:■
A line that rises to the right has a positive slope and a line that falls to the right has a negative slope.■
A horizontal line has a slope of 0 and a vertical line does not have a slope at all—it is undefined.■
Parallel lines have equal slopes.■
Perpendicular lines have slopes that are negative reciprocals.D a t a A n a l y s i s R e v i e w
Many questions on the GRE will test your ability to analyze data. Analyzing data can be in the form of sta-tistical analysis (as in using measures of central location), finding probability, and reading charts and graphs.All these topics, and a few more, are covered in the following section. Don’t worry, you are almost done! Thisis the last review section before practice problems. Sharpen your pencil and brush off your eraser one moretime before the fun begins. Next stop…statistical analysis!Measures of Central LocationThree important measures of central location will be tested on the GRE. The central location of a set ofnumeric values is defined by the value that appears most frequently (the mode), the number that representsthe middle value (the median), and/or the average of all the values (the mean).M
EAN AND
M
EDIAN
To find the average, or the mean, of a set of numbers, add all the numbers together and divide by the quan-tity of numbers in the set.Average =nu
s
m
um
be
o
r
f
o
v
f
a
v
lu
al
e
u
s
es
Example:
Find the average of 9, 4, 7, 6, and 4.+ 6 + 4
9 + 4 + 7
=
3
5
0
= 6
5
The denominator is 5 because there are 5 numbers in the set.To find the medianof a set of numbers, arrange the numbers in ascending order and find the middlevalue.■
If the set contains an odd number of elements, then simply choose the middle value.Find the median of the number set: 1, 5, 3, 7, 2.First, arrange the set in ascending order: 1, 2, 3, 5, 7.Then, choose the middle value: 3.The answer is 3.■
If the set contains an even number of elements, simply average the two middle values.Find the median of the number set: 1, 5, 3, 7, 2, 8.First, arrange the set in ascending order: 1, 2, 3, 5, 7, 8.Then, choose the middle values 3 and 5.Find the average of the numbers3 +
2
5
= 4.The answer is 4.M
ODE
The modeof a set of numbers is the number that occurs the greatest number of times.For the number set 1, 2, 5, 3, 4, 2, 3, 6, 3, 7, the number 3 is the mode because it occurs the most num-ber of times.Measures of DispersionMeasures of dispersion, or the spread of a number set, can be in many different forms. The two forms coveredon the GRE test are range and standard deviation.R
ANGE
The rangeof a data set is the greatest measurement minus the least measurement. For example, given the fol-lowing values: 5, 9, 14, 16, and 11, the range would be 16 – 5 = 11.S
TANDARD
D
EVIATION
As you can see, the range is affected by only the two most extreme values in the data set.Standard deviationis a measure of dispersion that is affected by every measurement. To find the standard deviation ofnmeas-urements, follow these steps: