Population
The whole of all items(scores, people, and so on) to be studied
Sample
A sample is a sub-collection of elements drawn from a population
In other words, a sample statistic, such as mean (average), represents our best estimate of the corresponding population parameter.
Measures of Position
measures of Central Tendency
A way to see where a certain data point or value falls in a sample or distribution
Mean
Most used measure of central tendency
- Average of all observations
- The sum of all the scores divided by the number of scores
- We can estimate the mean of population by using the mean of sample
Median
- This is the value of a variable such that half of the observations are above, and half are below this value i.e. this value divides the distribution into two groups of equal size
- When the number of observations is odd, the median is simply equal to the middle value.
- When there are exactly the same number of observations, we consider the median to be the average of the two values in the distribution’s middle
Interquartile Range (IQR)
The interquartile range tells you where the “middle fifty” is in a data set. While the range tells you where the beginning and end are in a set, the IQR shows you where the bulk of the “middling” values lie.
Outliers
Outliers are unusual values that fall outside of an expected range of values