Summarising and presenting data

Question 1

What are the 2 main categories of data?

Answer 1

Qualitative / categorical

Quantitative / numerical

Question 2

What types of qualitative data are there?

Answer 2

Unordered (male/female)

Ordered (small/ medium / large)

Question 3

What types of quantitative data are there?

Answer 3

Discrete (number of children in family)

Continuous (SBP)

Question 4

How would you examine the make-up of a sample of patients?

Answer 4

Using a frequency table

Question 5

When is cross-tabulation useful?

Answer 5

Way of exploring whether two qualitative variables have any association (e.g sex and smoking)

Question 6

What can bar charts and pie charts be used for?

Answer 6

To show proportions or percentages graphically

Question 7

What is the median?

Answer 7

central value, such that 50% of the data falls at either side

Question 8

What is the lower quartile?

Answer 8

Chosen to place 25% of the data below it

Question 9

What is the upper quartile?

Answer 9

chosen to place 75% of the data below it

Question 10

What is the inter-quartile range?

Answer 10

IQR

the difference between the 3rd and 1st quartiles, and quantifies the spread of the sample.

Question 11

What is the mean?

Answer 11

1/n(sigma)xI

Question 12

What is variance?

Answer 12

s2 = 1/(n-1) (sigma) (xi-mean)2

Question 13

How do the mean and median relate to each other when the sample of the data have a reasonable symmetrical distribution?

Answer 13

mean = median

Question 14

How do the mean and median relate to each other when the sample is positively skewed?

Answer 14

Mean >median

Question 15

How do the median and mean relate to each other when the sample is negatively skewed?

Answer 15

Mean < median

Question 16

What is a histogram a representation of?

Answer 16

The frequency distribution

Question 17

If a histogram is shifted to the right it indicates?

Answer 17

Negative skew

Question 18

If a histogram is shifted to the left it indicates?

Answer 18

positive skew

Question 19

When is a doxplot useful?

Answer 19

When there are not many data points

Question 20

How is positive skew seen in a box plot?

Answer 20

the distance from Q1 ro the median is much less from the median to Q3

Question 21

What graph should be used to compare to quantitative variables directly?

Answer 21

scatterplot

Question 22

When shouldn’t the mean be used to indicate the central value of the sample?

Answer 22

When the data is heavily skewed

Question 23

When are box-plots inappropriate?

Answer 23

With very small sample sizes (3-4 points)

Question 24

What are response variables?

Answer 24

these measures are used to describe the condition of an individual/subject (also called outcome measure or dependent variables?

Question 25

What are explanatory variables?

Answer 25

Those measures that might explain the condition of an individual/subject (also called predictor or independent variables)

Question 26

What are confounder variables?

Answer 26

Those measures that might obscure the relationship between response and explanatory variables. Associated with both the response variable and the explanatory variables