EIP - Summarising Data - Week 4

Question 1

Name and describe the two types of data. Give some general examples.

Answer 1

Qualitative - individuals can be divided into separate classes like gender, hair colour, eye colour.
Quantitative - numerical like number of students, height, weight

Question 2

List the two types of qualitative data.

Answer 2

Nominal - unordered like gender, hair colour

Ordinal - ordered - severity rating

Question 3

Define frequency.

Answer 3

The count of individuals with a particular quality

Question 4

What is the cumulative frequency of a value and what two types of data is it used for?

Answer 4

The number of subjects with values less than or equal to that value
Used only for ordinal qualitative variables or quantitative variables

Question 5

Define mode.

Answer 5

Most frequent value/observation

Question 6

In what distributions is the mode used?

Answer 6

Unimodal distributions only.

Question 7

Define positive and negative skews in a distribution.

Answer 7

Skewed positively - to the right (median to the left)

Skewed negatively - to the left (median to the right)

Question 8

What does the interquartile range give a measure of?

Answer 8

Statistical variability or spread

Question 9

What is the formula for the max and min values on a box and whisker plot?

Answer 9

Max = Q3 + 1.5 x IQR
Min = Q1 - 1.5 x IQR

Question 10

What is the mean commonly used to illustrate?

Answer 10

Central tendency

Question 11

What is range often used to illustrate?

Answer 11

Dispersion/spread/viability of the entire dataset

Question 12

What is the interquartile range used to illustrate?

Answer 12

The spread of the central 50% of the data

Question 13

What is the variance used to illustrate?

Answer 13

Spread of the data

Question 14

What is variance?

Answer 14

Sum of the squared deviations from the mean, divided by degrees of freedom (sample size minus one)

Question 15

What is standard deviation?/

Answer 15

Square root of the variance

Question 16

Define the following standard deviations in a normal distribution: 1, 2, and 3.

Answer 16

1 - 68%
2 - 95%
3 - 99.7%

Question 17

What is standard error of the mean and what value does it have when the sample size is large?

Answer 17

Standard deviation divided by the square root of the sample size
When sample size is large, SEM is small

Question 18

What is the standard error of the mean used to estimate? Why does it decrease with increasing sample size?

Answer 18

Used to estimate confidence limits for a mean.

When the sample size is very large, the SEM would become small since the sample mean would approach the population mean.