HadPop - Lecture 2 Flashcards
What are the types of variables
1) Categorical
- Ordinal
- Nominal
2) Numerical
- Continuous
- Discrete
What is a continuous variable?
A value that lies between a certain set of real numbers
e.g. height, temperature
What is a discrete variable?
A fixed value
e.g. number of cars
What is an ordinal variable?
Categorical data that can be ranked
e.g. mild moderate
What is a nominal variable?
Categorical data that cannot be ranked
What type of data can a histogram represent?
Continuous
How can you summarise frequency distribution graphs?
1) SHAPE
- UNIMODAL / BIMODAL
2) LOCATION
- MEAN
- MODE
- MEDIAN
3) SPREAD
- IQR
- SD
If that graph is skewed to the right, what does this tell us about the mean and median?
The mean is greater than the median
What is IQR?
Difference between the first and third quartile
How do you calculate variance?
Sum of the squares / degrees of freedom
How do you calculate SD from variance?
Take the square root of variance
What does SD tell us?
The spread of data around the mean value
What does a scatter plot show us?
The relationship between two continuous variables
How can we analyse a scatter plot?
1) Linear or non linear
2) Weak or strong (dots close together = strong)
3) Negative or positive
What is the correlation coefficient
a number between +1 and −1 calculated so as to represent the linear interdependence of two variables or sets of data.