BA 1 - Describing and Summarizing Data

Question 1

Axes of a histogram?

Answer 1

X-axis - bins corresponding to ranges of data;

Y-axis - frequency of observations falling into each bin.

Question 2

What’s an outlier?

Answer 2

An outlier is a value that falls far from the rest of the data.

Question 3

How do you examine the validity of an outlier?

Answer 3

i. Check if it’s valid, though unusual;
ii. Check for a data entry error; and
iii. Check if it was collected under different circumstances than the rest of the data.

Question 4

What do you do about an outlier?

Answer 4

Leave it; change it to its corrected value; or in extreme cases, delete it.

Question 5

Skewness

Answer 5

Skewness measures the degree of a graph’s asymmetry.

Question 6

What are descriptive statistics?

Answer 6

Summary measures that provide an overview of the data set without showing every data point.

Question 7

Mean

Answer 7

Sum of all data points divided by the number of data points

The mean is affected by outliers.

Question 8

Median

Answer 8

Middle value of the data set; i.e. 50th percentile.

When the number of values is even, it’s the average of the middle two values.

Question 9

Mode

Answer 9

Value that occurs most frequently

Question 10

Conditional mean

Answer 10

The mean of a subset of the data that includes all values satisfying a certain condition.

Question 11

Percentile value

Answer 11

Value beneath which a certain percentage of the data lie

i.e. 25th percentile is the smallest value that is greater than or equal to 25% of the data points.

Question 12

Range

Answer 12

Maximum value - Minimum value

Question 13

Relationship between standard deviation and variance?

Answer 13

SD = square root (Variance)

Question 14

What does variance measure?

Answer 14

Variance is a measure of how far each point is from the mean.

Question 15

Difference between populate and sample variance/sd?

Answer 15

For population, denominator is N; for sample, denominator is ‘n-1’

Question 16

Coefficient of Variation

Answer 16

SD/mean
Measures the standard deviation relative to the size of the mean.
It’s useful for comparing variation in different data sets.

Question 17

Kurtosis

Answer 17

Measure of flatness or sharpness of a distribution.

Low kurtosis => flat distribution

Question 18

[EXCEL] Mean

Answer 18

=AVERAGE(range)

Question 19

[EXCEL] Median

Answer 19

=MEDIAN(range)

Question 20

[EXCEL] Mode

Answer 20

=MODE.SNGL(range)

Question 21

[EXCEL] Conditional Mean

Answer 21

=AVERAGEIF(range,criteria,range)

Question 22

[EXCEL] Percentile

Answer 22

=PERCENTILE.INC(range,k)

33rd percentile => k = 0.33

Question 23

[EXCEL] Variance

Answer 23

=VAR.S(range)

Question 24

[EXCEL] Standard deviation

Answer 24

=STDEV.S(range)

Question 25

[EXCEL] Square root

Answer 25

=SQRT(number)

Question 26

[EXCEL] Number of values

Answer 26

=COUNT(range)

Question 27

[EXCEL] Range

Answer 27

=MAX(range) - =MIN(range)

Question 28

[EXCEL] Total

Answer 28

=SUM(range)

Question 29

[EXCEL] Correlation

Answer 29

=CORREL(range1,range2)

Question 30

Scatter plot

Answer 30

Shows the relationship between two variables as a visualization, though we cannot assume causal link.

Question 31

Correlation

Answer 31

• Measure that quantifies the strength of a linear relationship between two variables.
• Range - +1, -1. 0 = no linear relationship
• Does not imply causation
• Strongly influenced by outliers

Question 32

Hidden variables

Answer 32

Variable that is correlated with each of the two variables that are not fundamentally related to each other.

Question 33

Mediating variable

Answer 33

Variable which is affected by one variable, and in turn affects another.

Question 34

Time series

Answer 34

When one of the variables is time, the relationship is known as a time series

Question 35

Cross-sectional data

Answer 35

Cross-sectional data provide a snapshot of data across multiple groups at a given point in time.