Practical 1 Flashcards
Describe different types of data
Categorical - can be ordinal or nominal
Numerical - can be continuous or discrete
What is interval data?
Interval data refers to categorical data that can be ordered.
However as there are equal or > 5 points we can assume equidistance between these points hence this data is actually often used in numerical terms.
How are categorical and numerical descriptive statistics summarised
Numerical - histogram
Categorical - bar chart or pie chart (ordinal categorical data may be summarised on a histogram)
What is variance and define the equation for SD
Variance - distance from the mean
SD = Sum of (distance from the mean)2 / N - 1
Use N - 1 as an unbiased estimate of population variance
How are categorical data / numerical data reported in text
Categorical data N (frequency) and %. If skewed data may use min-max rather than %
Numerical - normally distributed mean (SD). Skewed - Median (IQR).
What is a variable?
A characteristic that varies
Why/When are statistics used?
Statistics are used to characteristic of interest in a sample of population
We infer the findings from the sample to the population (if the sample is representative)
Statistics are used as we can’t study the whole population - we sample - we can’t just count from the whole population - we use probability theory
We use statistics to understand why things vary?
The goal is to understand why things are not the same for everyone
When is ordinal data considered numerical - interval?
Ordinal data can be considered interval when at least 5 categories
4 or fewer ordinal data - categorical
Ordinal data is always skewed
How do discrete and continuous data vary?
Discrete data - can only have preset values, typically counts
Difficult - shoe size is discrete - even though decimal points there are distinct set of values
Continuous data can tae any value on a scale - typically measurements
