2] Descriptive Statistics Flashcards
What are the two main types of statistics
1: Descriptive statistics
2: Inferential statistics
What is the method of descriptive statistics
It is the method of simplifying, organising and summarising complex information.
Allowing research’s to summarise large quantities of data
What is inferential statistics
Is a method that use data collected from a sample to reach conclusions or make predictions or inferences about the population
They are used to infer the likelihood that the observed results can be generalised to the population or other samples of individuals
What are the two classes of descriptive statistics
1: Measure of central tendency
2: Measure of variation/dispersion
What is central tendency
It refers to the tendency data has to cluster around the centre point, it represents the average value given through a dataset
E.g: Average weight of a newborn baby
Central Tendency: What are the three main measures
1: Mean
2: Mode
3: Median
What is the mean
This is the most used measure of central tendency
It is used to calculate the average by adding each value together and then dividing it by the amount of values given
E.g: 4, 5, 7, 10
Added= 26
Dived= 26/4
Average= 6.5
The mean: Advantages and disadvantage
Advantages
1: Most useful
2: All values plau an equal role
Disadvantage
1: Can be effected by extreme values called outliers, screwing the average
What is the median
It represents the middle score in a dataset, when all the values have been ranked from lowest to highest
Rule of calculating the median
Rule 1: The data has an odd number of values
E.g: 6, 9, 3, 7, 12
Ordered: 3, 6, 7, 9, 12= 7
Rule 2: The data has an even number of values
E.g: 6, 9, 3, 7, 12, 8
Ordered: 3, 6, 7, 8, 9, 12= 7 and 8
Add them and divided by 2: 7+8= 15/2
Average= 7.5
The median: Advantages and disadvantage
Advantages
1: Simple to calculate and visualise
2: It is influenced less by extreme values
Disadvantages
1: We can do more with the mean in mathematical terms
2: It ignores most of the data
What is the mode
It is the value that appears most frequently in a data set and is mostly used for categorical variables but is the only method available for nominal data
There will be no mode if each values appears an equal amount of times
E.g: 200 people complete a survey on their favourite ice cream
Average: 62 out of 200 said chocolate making it the most frequently answered value
Types of modal distributions
1: Unimodal (1 value)
2: Bimodal (2 value)
3: Multimodal (2+ value)
The mode: Advantages and disadvantages
Advantages
1: Most simple form of central tendency
2: Only method for nominal data
Disadvantages
1: Less useful mathematically than the mean
When can the mean, mode and median be used
The mean:
Can be used for interval and ratio data
The mode:
Can be used for nominal, ordinal, interval and ratio data
The median
Can be used for ordinal, interval and ratio data
