Descriptive Statistics

Question 1

Define what is a measure of central tendency?

Answer 1

A measure that depicts an overall ‘central’ trend of a set of data.

(e.g- Mean, Median, Mode)

Question 2

Define Mean, how do you calculate it? and what kind of data is it used for?

Answer 2

Mean is the average value.
It is the sum of all numbers the data set, divided by how many numbers there are in the data set.

Used for Interval/ratio data.

Question 3

Define Median, how do you calculate it? and what kind of data is it used for?

Answer 3

Median is the middle score when the data is in numerical order.
(e.g the median of 1, 2, 3, 4, 5 is 3)

Used for Ordinal data.

Question 4

Define Mode, how do you calculate it? and what kind of data is it used for?

Answer 4

Mode is the most frequently occurring number in a data set.
(e.g the mode of 1, 2, 3, 4, 4, 5) is 4

Used for Nominal data

Question 5

Define what is measures of dispersion?

Answer 5

The most common measures of dispersion are Range and Standard deviation.
It describes the spread of data around a central value (mean, median, mode)

Question 6

How do you calculate Range?

Answer 6

Range = Greatest value - Least value

Question 7

How do you calculate Standard Deviation?

Answer 7

It is the average spread of values around the mean.

Example:
data set (2, 2, 4, 5, 32)

1)
2 + 2 + 4 + 5 + 32\5 = 9

2)
2-9 = -7
2-9 = -7
4-9 = -5
5-9 = -4
32-9 = 23

3)
-77 = 49
-77 = 49
-55 = 25
-44 = 16
23*23 = 529

4)
49 + 49 + 25 + 16 + 529 = 668

5)
668/5 = 133.6

6)
[square root of result] = 11.56 (2dp)

Question 8

How to calculate percentage?

Answer 8

Divide result by 100.
(e.g 38/100 = 0.38)

Question 9

Define Positive Correlation.

Answer 9

A Positive Correlation occurs when two variables are related and as one variable increases/decreases the other also increases/decreases

(e.g Both move in the same direction).

For example, you might expect to find a positive correlation between height and shoe size.

Question 10

Define Negative Correlation.

Answer 10

A Negative Correlation occurs when two variables are related and as one variable increases the other decreases.

For example, you might expect to find a negative correlation between the school performance of high school students and the amount of time they are absent from school.

Question 11

Define Zero Correlation.

Answer 11

Zero Correlation means that there is no relationship between the co-variables in a correlation study.