What Do The Whiskers Represent In A Box Plot?

What do points above and below the whiskers represent in a box plot?

However, the whiskers can represent several possible alternative values, among them: the minimum and maximum of all of the data (as in figure 2) one standard deviation above and below the mean of the data.

the 9th percentile and the 91st percentile..

How do you compare two box plots?

Guidelines for comparing boxplotsCompare the respective medians, to compare location.Compare the interquartile ranges (that is, the box lengths), to compare dispersion.Look at the overall spread as shown by the adjacent values. … Look for signs of skewness. … Look for potential outliers.

How do you determine outliers?

A commonly used rule says that a data point is an outlier if it is more than 1.5 ⋅ IQR 1.5\cdot \text{IQR} 1. 5⋅IQR1, point, 5, dot, start text, I, Q, R, end text above the third quartile or below the first quartile. Said differently, low outliers are below Q 1 − 1.5 ⋅ IQR \text{Q}_1-1.5\cdot\text{IQR} Q1−1.

What do the whiskers represent?

The left whisker represents the bottom 25% of the data, the left half of the box represents the second 25% , the right half of the box represents the third 25% , and the right whisker represents the top 25% .

How do you interpret a Boxplot?

Definitions. The median (middle quartile) marks the mid-point of the data and is shown by the line that divides the box into two parts. Half the scores are greater than or equal to this value and half are less. The middle “box” represents the middle 50% of scores for the group.

Which interval has the most data in it?

The interval 59–65 has more than 25% of the data so it has more data in it than the interval 66 through 70 which has 25% of the data. The middle 50% (middle half) of the data has a range of 5.5 inches.

Why is it important to identify outliers?

Identification of potential outliers is important for the following reasons. An outlier may indicate bad data. For example, the data may have been coded incorrectly or an experiment may not have been run correctly. … Outliers may be due to random variation or may indicate something scientifically interesting.

What do whiskers mean in a box plot?

In a box and whisker plot: the ends of the box are the upper and lower quartiles, so the box spans the interquartile range. the median is marked by a vertical line inside the box. the whiskers are the two lines outside the box that extend to the highest and lowest observations.

Which type of data would be best displayed in a box plot?

The box plot is a type of graph that is used to show the shape of a distribution, the central value, and its variability. It is often used in explanatory data analysis. The ends of the box are the upper and lower quartiles, and the total span is the interquartile range. So, the answer can be option D.

Why is a box plot better than a histogram?

Histograms and box plots are very similar in that they both help to visualize and describe numeric data. Although histograms are better in determining the underlying distribution of the data, box plots allow you to compare multiple data sets better than histograms as they are less detailed and take up less space.

How do you find the box and whisker plot?

The box in the box plot will show the median and the first and third quartiles. The length of the upper whisker is the largest value that is no greater than the third quartile plus 1.5 times the interquartile range. In this case, the third quartile plus 1.5 times IQR is 10 + 1.5*6 = 19.

What does it mean if a box plot is positively skewed?

Positively Skewed : For a distribution that is positively skewed, the box plot will show the median closer to the lower or bottom quartile. A distribution is considered “Positively Skewed” when mean > median. It means the data constitute higher frequency of high valued scores.

How do you describe the center of a box plot?

The median is indicated by the vertical line that runs down the center of the box. In the boxplot above, the median is between 4 and 6, around 5. Additionally, boxplots display two common measures of the variability or spread in a data set. … The middle half of a data set falls within the interquartile range.

How do you indicate the median in a box and whisker plot?

The far left of the chart (at the end of the left “whisker”) is the minimum (the smallest number in the set) and the far right is the maximum (the largest number in the set). Finally, the median is represented by a vertical bar in the center of the box.

How do you interpret outliers in a box plot?

When reviewing a box plot, an outlier is defined as a data point that is located outside the whiskers of the box plot. For example, outside 1.5 times the interquartile range above the upper quartile and below the lower quartile (Q1 – 1.5 * IQR or Q3 + 1.5 * IQR).