Today in reading book statistics i faced with some parameter as percentile,decile and so on. i want to share here discussion.

**Percentile** is a important parameter, i read definition from this link.I warned that for definition below parameter data should be sorted.

A

percentile(or acentile) is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations fall. For example, the 20th percentile is the value (or score) below which 20% of the observations may be found.

**Decile:**

In descriptive statistics, a

decileis any of the nine values that divide the sorted data into ten equal parts, so that each part represents 1/10 of the sample or population.^{[1]}A decile is one possible form of a quantile; others include the quartile and percentile.^{[2]}

**Quartile:**

n descriptive statistics, the

quartilesof a ranked set of data values are the three points that divide the data set into four equal groups, each group comprising a quarter of the data. A quartile is a type of quantile. The first quartile (Q_{1}) is defined as the middle number between the smallest number and the median of the data set. The second quartile (Q_{2}) is the median of the data. The third quartile (Q_{3}) is the middle value between the median and the highest value of the data set.

**Important Tip:In analysing of algorithms, mean and middle is not good parameter, some case it better consider some parameter like percentile,decile and…….**