Ch. 5: Graphs and Stats

Question 1

Central Tendency

Answer 1

Used to summarize data with 1 number

1) Mean
2) Median
3) Mode

Question 2

Measure of variability

Answer 2

Uses two numbers to summarize the data

1) IQR (Interquartile Range Q3-Q1)
2) Range (Max-Min)
3) Sum of squared deviations (x-mean) squared
4) Sample variance (SD-mean) squared/Total # observations -1

Question 3

Percentile

Answer 3

The position relative (compared to) others
Provides info about values relative to entrie data set
Suppose you scored in the 60th percentile on the GMAT. That means 60% of the other scores were below yours, while 40% of scores were above yours.

Question 4

Box Plots

Answer 4

Min
25th percentile (Q1)
Median (50th percentile, Q2)
75th percentile (Q3)
Max

Question 5

Interquartile Range

Answer 5

=Q3-Q1
Insensitive to outliers
Measures spread of middle 50%
Values that are far apart increase variability

Question 6

Range

Answer 6

=largest observation-smallest observation (Max-Min)
The simplest measure of variability
Sensitive to outliers
Better to use all the data and not just two points

Question 7

Sum of squared deviations

Answer 7

=(SD-mean) squared
Deviation=how far it is from the mean
Shows how much the data moves around versus staying in one place

Question 8

Sample variance

Answer 8

=(SD-mean) squared/total # observations - 1

(Sum of sqaured deviations)/total # observations - 1

Question 9

Standard deviation

Answer 9

=squared root of variance
radical s squared
Shows how tighly clustered the data is
Calculated by:
1) Empirical rule
2) Coefficient of variation
3) Z-score

Question 10

Empirical rule

Answer 10

Only for bell shaped histograms
68% fall within 1 Standard deviation lower=mean -SD upper=mean plus SD
95% fall within 2 SD lower= mean-2SD
99.7% fall within 3 SD

Question 11

Coefficient of variation (c of v)

Answer 11

=SD/mean

Question 12

Z score

Answer 12

= (x-mean)/SD

Shows how many SD’s we are from the mean