Basic descriptive statistics How to report statistics Plotting Flashcards
Lecture 3
What is central tendency?
A summary measure that attempts to describe a whole set of data with a single value that represents the middle or centre of its distribution.
What is the Arithmetic mean?
The sum of a series of numbers divided by the count of that series of numbers.
What is the median?
The middle observation in a set of data.
Use median – it stays the same whether data is normal/non-normal.
What is the mode?
The most common value in the dataset.
When is the median and mode useful?
Useful for datasets that have outliers or skewed distributions.
In a normal distribution, mean, median and mode are equal or very similar.
The mean is preferred.
In a skewed distribution, the mean and median are not equal.
The median is preferred.
What is varience?
gives an actual value to how much the numbers in a dataset vary from the mean.
What is the standard deviation?
measures how far apart numbers are in a dataset.
Standard deviation is the square root of the variance and is expressed in the same units as the data set.
Standard deviation is calculated from the variance.
The standard deviation is graphically depicted as a bell curve’s width around the mean of a data set. The wider the curve, the larger a data set’s standard deviation from the mean.
Why is varation useful?
To compare samples, we need a standardized measure of the variation within each sample
We can then predict the proportions of each sample that are:
Greater or lower than a single value
Likely to overlap with another sample/samples.
How can we obtain one standardized measure of all these deviations from the mean?
standard deviation
What is standard error?
https://www.youtube.com/watch?v=A82brFpdr9g
The standard deviation of the distribution of sample means is called the standard error (SE).
Enables us to assess how reliably a ‘sample mean’ estimates the ‘population mean’ from which the sample is drawn.
