Quick Answer: What Do Quartiles Tell Us?

What is the importance of quartile?

Quartiles tell us about the spread of a data set by breaking the data set into quarters, just like the median breaks it in half.

For example, consider the marks of the 100 students below, which have been ordered from the lowest to the highest scores, and the quartiles highlighted in red..

Is the First Quartile the same as the 25th percentile?

The values that divide a rank-ordered set of data into 100 equal parts are called percentiles. … Quartiles divide data into quarters. The first quartile (Q1 ) is the 25th percentile, the second quartile (Q2 or median) is 50 th percentile, and the third quartile (Q3 ) is the the 75 th percentile.

Where do we use quartile?

Quartiles often are used in sales and survey data to divide populations into groups. For example, you can use QUARTILE to find the top 25 percent of incomes in a population.

What are the 4 quartiles?

Generally, the data is arranged from smallest to largest: First quartile: the lowest 25% of numbers. Second quartile: between 25.1% and 50% (up to the median) Third quartile: 51% to 75% (above the median) Fourth quartile: the highest 25% of numbers.

How are quartiles used in real life?

Some companies use the quartiles to benchmark other companies. For example, the median company pay for a given position is set at the first quartile of the top 20 companies in that region. The quartiles and IQR information is typically used when you create a box-plot of your data set.

What does the first quartile represent?

The first quartile, denoted by Q1 , is the median of the lower half of the data set. This means that about 25% of the numbers in the data set lie below Q1 and about 75% lie above Q1 . The third quartile, denoted by Q3 , is the median of the upper half of the data set.

What does the interquartile range tell you?

The “interquartile range”, abbreviated “IQR”, is just the width of the box in the box-and-whisker plot. That is, IQR = Q3 – Q1 . … The IQR tells how spread out the “middle” values are; it can also be used to tell when some of the other values are “too far” from the central value.

What does q1 and q3 mean?

Q1 is the median (the middle) of the lower half of the data, and Q3 is the median (the middle) of the upper half of the data. (3, 5, 7, 8, 9), | (11, 15, 16, 20, 21). Q1 = 7 and Q3 = 16. Step 5: Subtract Q1 from Q3.

Why is the interquartile range important?

Besides being a less sensitive measure of the spread of a data set, the interquartile range has another important use. Due to its resistance to outliers, the interquartile range is useful in identifying when a value is an outlier. The interquartile range rule is what informs us whether we have a mild or strong outlier.

What does upper quartile mean?

The upper quartile (sometimes called Q3) is the number dividing the third and fourth quartile. The upper quartile can also be thought of as the median of the upper half of the numbers. The upper quartile is also called the 75th percentile; it splits the lowest 75% of data from the highest 25%.

What does the lower quartile tell you?

The lower quartile value is the median of the lower half of the data. The upper quartile value is the median of the upper half of the data.

How do you analyze quartiles?

Using Quartile Summary Statistics to Analyze Variability Quartiles represent the value for which 25% of the data is below (Q1) and the value for which 25% of the data is above (Q3). The Interquartile Range (IQR) is the difference between these two quartiles (Q3 – Q1 = IQR).

What is the 5 number summary in stats?

A summary consists of five values: the most extreme values in the data set (the maximum and minimum values), the lower and upper quartiles, and the median. These values are presented together and ordered from lowest to highest: minimum value, lower quartile (Q1), median value (Q2), upper quartile (Q3), maximum value.

How do you find quartiles examples?

Quartiles are the values that divide a list of numbers into quarters: Put the list of numbers in order. Then cut the list into four equal parts….In this case all the quartiles are between numbers:Quartile 1 (Q1) = (4+4)/2 = 4.Quartile 2 (Q2) = (10+11)/2 = 10.5.Quartile 3 (Q3) = (14+16)/2 = 15.

How do you find the upper and lower quartiles?

AnswersThe values in ascending order are: Median = (12th + first) ÷ 2. … Range = difference between the highest and lowest values. = 57 – 1. … Lower quartile = value of middle of first half of data Q1 = the median of 1, 11, 15, 19, 20, 24. … Upper quartile = value of middle of second half of data Q3 … Interquartile range = Q3–Q1