Summarizing and displaying data

Question 1

what is a Variable?

Answer 1

A value that takes different values or categories ie. blood pressure, nationality

Question 2

What are the types of measurement scales?

Answer 2

1. Numerical = continuous/ discrete
2. categorical = nominal/ordinal

Question 3

What are the types of variables?

Answer 3

1. numerical
   -continuous = continuous on a number line (0,0.1,0.2)
   -discrete = whole numbers (1,2,3)
2. categorical
   -nominal = variables have no order (blood group, nationality)
   -ordinal = variables have an order (BMI, disease severity)
   -dichotomous/binary = only two values exist (dead or alive)

Question 4

What type of graph is best used for categorical data?

Answer 4

horizontal bar graph

Question 5

What type of graph is best used for a small amount of data in continuous scale ?

Answer 5

Small amounts of data = dot plot

Question 6

What is needed when data sets become too large?

Answer 6

summaries

Question 7

What are the methods of summarizing data for numerical and categorical data?

Answer 7

1. numerical
   a. measures of centrality
   -means, modes, medians
   b. measures of dispersion
   -standard deviation, IQR, range, variance
2. categorical
   a. counts/frequencies
   b. proportions/percentages

Question 8

What are other names for the measures of centrality

Answer 8

also called measures of location or measures of central tendency

Question 9

What do measures of dispersion/variability refer to?

Answer 9

how spread out the data is

Question 10

What is the most commonly used measure of dispersion?

Answer 10

standard deviation

Question 11

What does a lower value of standard deviation mean? higher value?

Answer 11

lower = each data point is closer to the mean and to each other / higher = each data point is farther from the mean and from each other

Question 12

Define the quartiles.

Answer 12

Q1: 25% of the data lie below Q1 (and 75% is above Q1)
Q2 is the same as median = divides the data into two halves (50% above, 50% below)
Q3: 25% of the data lie above Q3 (and 75% is below Q3)

Question 13

Define quartiles in relation to percentages.

Answer 13

Q1 = 25%
Q2 = 50%
Q3 = 75%

Question 14

What is the interquartile range?

Answer 14

Q3 - Q1

Question 15

When are the median and IQRs used? When are the mean and standard deviation used?

Answer 15

1. when distribution of values is not symmetric about the center = with outliers
2. used without outliers

Question 16

What is an outlier